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Emmissions-Spectra. 


Solar 

Spectrum 


Nitrogen 

Band \ 
Spectrum/ 


Oxygen 


Hydrogen 


Barium 


Calcium 


Strontium 


Indium 


Thallium 


Rubidium 


. Caesium 


Potassium 


Lithium 




Sodium 















































































Qualitative Chemical 

Analysis 


A LABORATORY GUIDE 


BY 


WILFRED WELDAY SCOTT, A.M. 

«« ' 


INDUSTRIAL RESEARCH AND CHEMICAL ENGINEERING, 

GENERAL CHEMICAL COMPANY 
EDITOR, “ STANDARD METHODS OF CHEMICAL ANALYSIS ” 
FORMERLY, CHIEF CHEMIST, BALDWIN LOCOMOTIVE WORKS, AND PROFESSOR 

OF CHEMISTRY, MORNINGSTDE COLLEGE 


ILLUSTRATED 


FOURTH EDITION 

REVISED AND ENLARGED 



NEW YORK 


D. VAN NOSTRAND COMPANY 


EIGHT WARREN STREET 
1921 













Copyright, 1910, 1913,1918 

BY 

D. VAN NOSTRAND COMPANY 


Copyright, 1921 

BY 

D. VAN NOSTRAND COMPANY 


MAR 28 i92l 

§>CU611336 



THIS BOOK 


IS AFFECTIONATELY DEDICATED 
TO 

MY MOTHER 
jfflarg pteabetI| 









PREFACE TO THE FOURTH EDITION 

In this edition, a number of tests have been added to the 
section on acids, notably for thiosulphates and sulphites. 
Certain misprints appearing in the Third Edition have been 
corrected and several changes made in the text. The Author 
would specially mention Prof. Guy Y. Williams, University of 
Oklahoma, for his assistance in the revision of the book. 

w. w. s. 


COYTESVILLE, N. J., 

January, 1921. 












PREFACE TO THE FIRST EDITION 


The purpose of this manual is to furnish a practical up-to-date 
guide for students studying qualitative analysis. The text em¬ 
bodies such methods of procedure in analysis as have been thor¬ 
oughly tested and have proven themselves to be of practical value. 

The text is divided into five parts. Part I, the Introduction, 
discusses briefly the ionic hypothesis, theory of solution and those 
principles of physical chemistry which are of frequent application 
in qualitative analysis. Methods and precautions to be observed 
in laboratory work are given. Part II is a systematic study of the 
bases. The following order is observed not only in the study of 
the metallic ions, but also of the acid radicals; a brief description 
of the members of the group, special tests including only those that 
serve to distinguish the substance, preliminary reactions leading 
up to the detection of material in a combination, separation of 
the members of the group, a discussion of the methods used, and a 
final list of questions covering certain important facts concerning 
the group. Part III takes up the study of the acid radicals. 
Part IV is a systematic method of analyzing an unknown sub¬ 
stance, beginning first with preliminary tests to gain valuable 
inferences that will shorten the methods, then analyzing the 
substance first for the bases it may contain, and finally its acids. 
Part V consists of tables of reactions for bases and acids. In 
Part II only such reactions were studied as lead directly to an 
isolation and detection of the substance, Part V is designed to 
meet the want of those desiring a more extended list of tests. 
The tabular form is easily followed and occupies but small space, 
affording an excellent reference chart for the analyst. The text 
is concluded with directions for preparing reagents used in the 
course and a table of solubilities. 

vii 






PREFACE 


viii 

The author believes that, since a course in qualitative analy¬ 
sis is preparatory to quantitative analysis, emphasis should be 
placed on such methods as can be used in quantitative deter¬ 
minations. The student should be taught the importance of 
careful, cleanly methods which are so necessary for reliable results. 
The technic the student develops in this course will cling to him 
in after years. No subject brings out what is in an individual 
more emphatically than does a course in qualitative analysis. 
His patience is thoroughly tested, for he learns that the laws of 
nature are inexorable, and in order to get certain results con¬ 
ditions bringing them about must be closely adhered to or the 
tests will fail. The author has endeavored to make the directions 
of procedure explicit, so that they can readily be followed by a 
beginner. No direction, however explicit, can supply the place 
of an instructor, and it is sincerely hoped that students taking 
up the work will receive competent supervision. 

Wilfred W. Scott. 

Philadelphia, Pa., 

January, 1911 . 








CONTENTS 


PART I 

PAGE 

Introduction. Terms Employed. Fundamental Principles; Theory 
r Solution, Electrolysis, Hydrolysis, Complex Ions, Color Reactions, 
faemical Equilibrium, Reversible Reactions, Mass Action, Repression 
f Ionization—Common Ion Effect, Solubility Product, Electromotive 
r Potential Series. Laboratory Directions; Dry Reactions; Heat- 
ig the Substance, Blowpipe Tests, Oxidation and Reduction, Film 
Tests, Flame Tests, Borax Bead Tests; Wet Reactions; Filtration, 
faction, Asbestos Filter, Evaporation, Cleaning of Apparatus, Record¬ 
ing Results, Suggestions. 1 

PART II 

The Metals. The Groups, Reactions of the Groups, Separation of 
he Groups, Tabular Outline of Separation, Notes on Separation. 26 

Hydrogen Chloride Group; Description of the Elements—Lead, 
VIercury and Silver; Laboratory Tests and Chemical Reactions of the 

I jlroup; Procedure for Separation of the Group; Notes on the Procedure, 

fteview. 33 

Hydrogen Sulphide Group; Description of the Elements Bismuth, 
Cadmium, Copper, Antimony, Arsenic, Tin, with Characteristic Tests 
ind Laboratory Exercises on their Chemical Reactions; Separation of 
the Members of the Group, Soluble and Insoluble Subdivisions; Notes 

on the Separations, Review. 45 

Ammonium Sulphide Group; Description of the Elements Aluminum, 
Chromium, Cobalt, Iron, Manganese, Nickel, Zinc, with Character¬ 
istic Tests and Exercises on their Chemical Reactions; Separation 
of the Members of the Group—Ammonium Sulphide, Hydroxide, 


Basic Acetate Methods; Notes on Procedures; Review. 81 

Ammonium Carbonate Group; Description of the Elements 
Barium, Calcium and Strontium with their Characteristic Tests and 
Exercises on their Chemical Reactions; Separation of the Group, 

Notes on the Separation; Review. 125 

ix 














X 


CONTENTS 


Soluble Basic Group; Description of the Elements Magnesium, 
Potassium and Sodium, and of the Ammonium Radical; Exercises on 
the Reactions; Method of Detection in a Mixture of the Alaklies; 
Notes on the Separation; Review. 

PART I'll 

The Acids. Survey of the Groups. The Volatile Acid Group; De¬ 
scription of the Members H2CO3, (HCN)HCIO, HNO2, H 2 Si03, 
H 2 S, H2SO3, H2S2O3; Exercises on Their Chemical Tests; Separa¬ 
tion; Review. 

Silver Nitrate Group; Description of the Acids HC1, HBr, HI, 
HCN, H 4 Fe(CN) 6 , H 3 Fe(CN) 6 , HSCN; Exercises on Tests of the 
Acids, Analysis of the Group, Separation of the Halogens, Review.... 

Barium Chloride Group; Description of the Acids H 2 B0 3 , HF, 
H 3 POi, H 2 S0 4 , with Exercises on Their Characteristic Tests; Analysis 

of the Group, Review. 

Soluble Acid Group; Description of the Acids HC 10 3 , HN0 3 , 
HMn0 4 , with Exercises on Tests of the Group; Analysis and Review. 

Organic Acids; Description of the Acids HC2H3O2, H2C2O4, 
H2C7H4O3, H2C4H4O,, with Exercises on Characteristic Tests; Review. 
Studies of Reaction Limits. 


PART IV 

Systematic Analysis of a Substance; Preliminary Examination of 
a Solid Substance; Combustion Tube Tests, Reduction Tests on 

Charcoal, Flame Tests, Borax Bead Tests, Sulphuric Acid Tests. 

Preliminary Examination of a Liquid; Analysis of the Metals; 
Preparation of the Solution, Substances Soluble in Water, Acid-sol¬ 
uble Substance, Refractory Substances Insoluble in Acids, Alloys; 

Table of Separations. 

Analysis of the Acids; Rules on Solubilities; Preparation of the 
Solution for Acid Analysis, Preliminary Tests of the Groups, Tab¬ 
ulated Table of Tests. 

Interpretation of Results. 


PART V 

Tables of Reactions of the Metals and the Acids. Table of Com¬ 
pounds, Table of Solubilities. 


PA Ol 

13< 

15 ; 

17< 

1 * 

20 ( 

20 ' 

21 

221 

221 

23 < 

24( 














CONTENTS 


xi 


PART VI 

PAGE 


The Less Common Elements. Rarer Elements of the Hydrogen 
ulphide Group; Properties and Tests for Gold, Platinum, Osmium, 
'alladium, Rhodium, Ruthenium, Molybdenum, Selenium, Tellurium, 

'ungsten. 293 

Rarer Elements of the Ammonium Sulphide Group. Properties 
nd Detection of Cerium and Other Rare Earths; Properties and 
)etection of Glucinum (Berillium), Titanium, Uranium, Vanadium, 

irconium. 310 

The Rare Metals of the Alkali Group. Properties and Tests for 

<ithium, Rubidium, Caesium. 322 

Mendeleef’s Periodic System of the Elements. International 
atomic Weights. Reagents in Solution and Solid Reagents, Prepa- 
ation of Special Reagents.324 

Qdex. 331 

- 






















QUALITATIVE ANALYSIS 


PART I 

INTRODUCTION 

In the study of General Inorganic Chemistry the student 
has become familiar with the occurrence, physical and chemical 
properties of the more important elements and their combinations 
as acids, bases and salts. He has made a study of methods by 
which the common elements are isolated, as well as the synthetic 
processes of obtaining certain combinations. In the laboratory 
experiments he has become accustomed to handling such apparatus 
as is involved in the study of these substances. He is now ready 
to apply this knowledge to the field of Analytical Chemistry, 
which is concerned with the determination of the kinds of matter, 
and the quantity present in a given substance. The systematic 
examination of a substance to identify its constituents and ascer¬ 
tain their amounts is known by the term “Analysis.” Qualitative 
Analysis deals with the identification of matter, Quantitative 
Analysis with the quantity of one or more of the constituents 
present in the material examined. The purpose of this book is to 
furnish information which will enable the analyst to distinguish 
substances one from another. 

TERMS EMPLOYED IN QUALITATITE ANALYSIS 

Reagent.—This is a substance employed in the process of 
separation of elements or in their isolation and detection. 

Precipitation.—When an aqueous solution of a reagent is 
added to a solution of a substance undergoing examination, it 






2 


QUALITATIVE ANALYSIS 




may cause a readjustment of combinations that will produo 
an insoluble compound, which will be thrown out of solutioi 
or “ precipitate ” as a solid. In describing precipitates th< 
following terms are used: flocculent , when the precipitate ha 
a flaky appearance; curdy , when it appears like milk curds 
heavy, when it settles rapidly; granular , when it appears h 
fine grains; and crystalline, when transparent crystals are evi 
dent. 

Reaction.—This is a chemical process involving a change ii 
a substance. This process may be represented by chemics 
symbols in the form of an “ equation” For example whe: 
hydrochloric acid is added to a solution of silver nitrate, a reactio 
takes place and the precipitate of silver chloride results, this i 
expressed by the equation AgN 03 +HCl= l AgCl+HN 03 . 

Filtration.—If the turbid solution, formed by precipitatio 
of a substance, is poured on to a filter paper, placed in a funne 
the operation is called “ filtration.” The liquid passing throug 
the filter is known as the “filtrate” and contains the solub' 
matter, the substance remaining on the filter paper is the “ pr< 
cipiiate ” or “ residue” 

When water is added to the residue on the filter paper to remo's 
soluble constituents, and the extract removed from the residu 
the process is spoken of as “ washing ” the precipitate or residu 

Decantation.—This facilitates washing of a precipitate. Th 
can best be accomplished by allowing the granular compour 
to settle, pouring off the clear, supernatant liquid on to the w< 
filter, adding more of the washing reagent (generally pure water 
stirring, allowing the precipitate to settle, pouring off the liquf 
and when the salt has been sufficiently washed, pouring the la 
washing with the precipitate on the filter. The washing solutic 
should be added to the salt in small portions, to lessen its tendenc 
to dissolve. The residue should be washed down from the waj 
of the filter into the apex of the cone. 

Digestion.—When two products are nuxed hot or cold, ai 







INTRODUCTION 


3 


[lowed to react some time with frequent stirring, the process is 
Doken of as “ digestion.” 

Appearance of Solution. —A solution is said to be “ dear ” 
hen it does not contain suspended matter. The solution may 
e colorless or colored. 

Neutralization. —When a base and acid in solution are mixed 
1 such a proportion that the resulting solution does not affect an 
idicator such as litmus, the solution is said to be neutral. 

Pseudo-solutions. —Certain amorphous substances called col- 
)ids dissolve to form pseudo-solutions in water. Arsenous 
llphide, the hydroxides of aluminum and iron, are examples, 
'he addition of a salt solution or an acid to pseudo-solutions will 
recipitate the colloids. Since colloids become denser and less 
)luble at high temperatures, it is well to precipitate them from 
ot solutions. 

Oxidation and Reduction. —Oxidation is the reaction by which 
xygen or some non-metallic element is added to a substance, or 
ydrogen or some metallic substance removed. Reduction is the 
rocess in which oxygen or some non-metallic element is removed 
om a compound, or hydrogen added. By oxidation the charge 
f a cation may be increased and by reduction it may be dimin- 
;hed. 

Examples: 

Oxidation . 2 FeS04+H2S04+0 = Fe2(S04)3-f H 2 O. Valence 
'e ++ raised to Fe +++ . 

Reduction. FeCl 3 +H = FeCl 2 +HCl. Valence Fe +++ lowered 
) Fe ++ . 

Amphoteric Electrolytes. —These are substances which act as 
sids in the presence of strong bases or as bases in the presence 
i f strong acids. Aluminum hydroxide is an example of an ampho¬ 
ric electrolyte. It may ionized in two ways: 

Al(OH ) 3 nr Al(OH ) 3 

Hj+AIO,—- _| |_Al+++(OH),- 


! 







4 


QUALITATIVE ANALYSIS 


Strong acids, owing to their free hydrogen cations, repress th 
H+ion of the aluminate so that ionization takes place according to 
the reaction on the right; on the other hand, an addition of i 
strong base, owing to the concentration of the OH - anions in th 
solution, prevents the ionization of the weak base; hence th 
reaction represented on the left takes place. (See pages 3 and 12. 

FUNDAMENTAL PRINCIPLES 

For understanding principles of analytical chemistry it i 
advisable to learn certain fundamental laws governing chemics 
action and physical changes in solution. 

Theory of Solution.—Solutions are homogeneous mixture 
which cannot be separated into their constituent parts by mechar 
ical means. We may have solutions of gases in gases, solutior 
of liquids in gases, solutions of solids in gases, solutions of gase 
in liquids, solutions of liquids in liquids, and solutions of solids i 
liquids. The quantity of the substance that will dissolve in a give 
solvent depends not only upon the amount of the solvent, but upo 
the nature of the solute and the solvent and upon conditions ( 
temperature and pressure. One liter of water, for example, wi 
dissolve 1148 liters of NH 3 , 503 liters of HC1, 79.8 liters of SO 
1800 cc. of CO 2 , 41.2 cc. of 0, 21.2 cc. of H, and 20 cc. of N, th 
temperature being 0° and the pressure 760 mm. Raising th 
presssure increases the solubility of the gas, but raising the ten 
perature lowers its solubility; in cases of solids, however, rise < 
temperature increases solubility, with a few exceptions. Upo 
the fact that no two substances have the same dissolving value- 
and this value depends upon certain conditions—are based man 
of the processes of separation and detection of the elements i 
qualitative analysis. The student has learned that when acid 
bases, and salts are brought into an aqueous solution, they underg 
a peculiar kind of disintegration, which does not stop with th 
formation of molecules, but extends to the dissociation of mol< 
cules into their component parts, called ions, to a greater or lef 


INTRODUCTION 


5 


xtent according to the nature of the substance. The dissocia- 
ion increases with the rise of temperature and with dilution, 
nd decreases with concentration. Since electrical conductivity 
nd chemical activity depend upon the ions, substances ionizing 
eadily are good conductors and chemically active. Nitric, 
ydrochloric, and sulphuric acids are more active chemically than 
cetic, hydrocyanic, and silicic acids, since they ionize much more 
sadily. Likewise potassium hydroxide and sodium hydroxide, 
diich are highly ionized in solution, are stronger bases than 
mmonium hydroxide or organic bases, which dissociate feebly. 1 
"he activity of acids is due to the hydrogen cation H + , and that of 
ases to hydroxyl anion OH~. Most of the reactions studied in 
ualitative analysis are ion reactions. It is necessary to recog- 
ize the ions rather than the compounds as a whole. In practi- 
ally all the salts the basic and acid components show exactly 
i tie same reactions, no matter in what combinations these radicals 
'lay be. For example, chlorine is precipitated as silver chloride 
dien silver nitrate is added to any soluble chloride which, ionized, 
ives a chloride anion. NaCI, KC1, CuCL, BaCL, FeCL readily 
'sspond to the silver test for chlorine. Likewise copper is pre- 
ipitated by hydrogen sulphide as copper sulphide from the solu- 
lon of a soluble copper salt such as CuSC>4, Cu(NC>3)2, CuCL, etc. 
"he identity of the substance is maintained in all its manifold 
ombinations as long as it can form free ions in solution. The 
ase of complex ions will be dealt with later. 

The student has learned that the ions and molecules in a sob- 
on act in a manner very similar to the molecules of a gas in a 
losed vessel. The activity of these particles produces what is 
nown as osmotic pressure, and enables the substance to diffuse 
1 the solvent. This osmotic pressure, as in case of a gas, is 
lcreased by heat and by the concentration of the particles. The 

1 Relative degrees of ionization, NaOH and KOH = 1. 

Ca(OH) 2 , Ba(OH) 2 and Sr(OH) 2 = .03. 

NH 4 OH = .O4I8; H 2 0 = .0i 6 2. 





6 


QUALITATIVE ANALYSIS 


boiling and freezing points of a solution are governed by the numb( 
of the particles in the solution; and since molecules and ions ac 
alike in this particular, substances that dissociate into ion* 
the electrolytes have a greater effect than substances that d 
not dissociate, the non-electrolytes. 

Electrolysis.—The theory regarding the phenomena that tak 
place when an electric current enters an ionized solution is base< 
on the belief that the ions are electrically charged bodies with j 
definite amount of electricity according to the nature of the ion 
For example, if a univalent metallic cation carries, say, one uni 
charge of electricity, then a divalent cation will hold two units o: 
electricity, in both cases the charges being positive; and again, if i 
monovalent acid radical or anion carries a unit charge of negative 
electricity, then the bivalent anion would hold two units. Scienti¬ 
fic investigation shows that each ion carries, for its formula weighl 
in grams, 96,580 coulombs per equivalent. The solution of a 
salt is neutral when the negative and positive electric charges 
present are equal in magnitude and opposite in effect. When 
electrodes are immersed in the solution, the anions are attracted 
to the anode, where their charge is neutralized, leaving them in 
the form of ordinary radicals, which either escape as molecules 
in the form of gas or unite with the solvent to form acids. Like¬ 
wise the cations attracted to the cathode neutralize their charge, 
becoming ordinary atoms, which combine with their own kind, 
forming molecules of metals, which carry no charge and which in 
turn may react with the solvent, forming bases. 

Example: 

(a) Na 2 S0 4 in solution ionizes, forming Na 2 + S0 4 —. 

(b) Electrodes immersed in the solution 

Cathode (-) *-2Na+ | S0 4 —-> Anode (+). 

(c) With charges neutralized. 

At cathode 2Na+ reacts with solvent 2HOH-> f H 2 +2NaOH 




INTRODUCTION 


7 


At anode 2(S(>4— )+ 2 HOH— > t O2+2H2SO4. Oxygen es- 
apes and the acid ionizes. 

(d) The acid and base now react, since their ions H+ and OH“ 
ombine to form the undissociated compound, water. 

2NaOH<=±2Na+ 20H" 

H 2 SO 4 ?=*S0 4 — 2H+ 

IT i 

Na 2 S0 4 2H*0 

'he ions are now ready to repeat the process, so that the reaction 
; a continuous one as long as the solvent remains, so that in 
3 ality the electrolysis of water takes place. Metals which do 
ot decompose water collect around the cathode as a deposit, 
.dvantage is taken of this in the important electrolytic processes, 
ich as electroplating, refining of metals, etc., and in processes of 
nalytical chemistry. 

Hydrolysis. —Water is itself very feebly dissociated into the 
>ns H+ and OH“. Pure water at room temperature is one ten 
lillionth normal with reference to hydrogen and hydroxyl ions. 
Tow if a salt of a strong base (i.e. one whose solution gives a 
igh OH“ concentration) and a weak acid (i.e. one whose solution 
ives a low H + concentration) is dissolved in water, the solution 
ill react alkaline; and again if a salt of a strong acid and a weak 
ase are dissolved in water, the solution will react acid. The 
ction is due to hydrolysis, a double decomposition involving the 
issociation of water. The H + cations of the water in the first 
ase react with the weak acid anion forming the undissociated 
cid, while the OH - anions of the water, no longer bound, give 
le solution a definite basic reaction. 

Thus when KCN, a salt of a strong base KOH, and a weak 
2 id HCN is dissolved in water the reaction may be represented 
3 follows: 

KCN (Solid) <=±KCN (Solution) *=±K + CN“ 

HOH^tOH- H+ 

. IT IT 

KOH HCN 




8 


QUALITATIVE ANALYSIS 


In the second case the OH~ anions of the water react with the 
weak base to form the undissociated base, and the H + cations, 

The reaction may be represented as follows: 

FeCl 3 (Solid) FeCl 3 (Solution) Fe+ + + 3C1~ 

3HOH *=>30H- 3H+ 

IT IT 

Fe(OH), 3HC1 

We observe the reaction by the formation of a brown precipi¬ 
tate, ferric hydroxide. 

Complex Ions.—There are cases where the elements do no ; 
respond to their tests, since they are combined with some other 
element or elements in the form of a complex ion. For example, 
chlorine in the compound potassium chlorate does not give a pre¬ 
cipitate with silver nitrate, as it remains combined with the 
chlorate anion in the form C 103 ~ e.g. KCIO3 ionizes into K + C 103 ". 
A test for C 103 - will, of course, indicate the presence of chlorine, 
but in order to test directly for this element the chlorate must 
be decomposed to a chloride which gives a free chlorine ion. 
Likewise, iron combined as a ferrocyanide or a ferricyanide will 
not respond to its tests. The salt K 4 Fe(CN) 6 ionizes thus, 
K 4 + Fe(CN)6 . The ferrocyanide test will indicate iron, but 
a direct test can only be obtained by liberating the iron from the 
complex anion by decomposing the ferrocyanide. These facts 
go further to confirm the statement that analysis deals with ions 
whose behavior makes possible their identification. 

Color Reactions.—The color of precipitates or of ions in solution 
frequently is characteristic. Color changes may be due either to 
a non-ionized condition of a substance or to ions. The indicator 
phenolphthalein, existing as an un-ionized acid in the presence of 
free hydrogen ions of another acid, is colorless, whereas its anion 
is a deep purple which becomes evident in the presence of the 
hydroxyl anions of a base. Undissociated litmus acid is red, its 
anion is blue. Un-ionized ferric hydroxide is brown, Fe +++ is 
pale yellow, Fe++ is green, Fe (CN) 6 -yellow, Fe(C 2 0 4 ) 2 — 





INTRODUCTION 


9 


ed. Though CNS“ is colorless, the iron salt which dissociates 
ut slightly is a deep red. The copper ion Cu ++ is blue, 
hi(NH 3 ) 4 ++ deep blue, which is reduced by the addition of 
CCN to the cuprous ion Cu, which has no color. Co ++ ions 
re pink; Ni ++ are green. A number of the ions have no color, 
.g. Ca++, Mg++, OH", Cl- Br", S0 4 “, N0 2 -, C10 3 - Oxida- 
ion or reduction may cause a color change; monovalent per- 
langanate ion is a deep blue, whereas the divalent cation Mn + + 

3 faint pink; the green chromium salts oxidized form the yellow 
hromates; Cr ++ cation green changes to Cr0 4 anion yellow, 
^he phenomenon of fluorescence is attributed to the ions of a 
olution. 

Chemical Equilibrium—Reversible Reactions. —Our attention 
hus far has been directed towards simple reactions. The ques- 
ion that now arises is, what reaction takes place in a mixture of 
wo soluble salts such as potassium carbonate and sodium sulphate 
yhere no chemical change is evident? For a reply we turn again 
o the ionic theory; since both of these salts are highly ionized as 
yell as the salts formed by an interchange of the radicals so that 
, less dissociated combination cannot take place, we conclude 
hat the salts simply dissociate into their ions, in sufficiently 
lilute solutions, and the products K + , Na + , S0 4 , and CO3 

:xist in the solution. It makes little difference whether K 2 CO 3 
md Na 2 S0 4 or K 2 S0 4 and Na 2 C0 3 are used; the solutions in 
ither case will be the same, the conditions being constant. 

A second case arises where it is possible for a product to form 
n a mixture, which dissociates to a less degree than the original 
ubstances in the solution. A reaction here may be evident either 
>y a precipitate forming, or a gas being evolved, or a color reaction, 
j>r by the formation of an invisible, slightly dissociated soluble 
compound, the reaction being recognized by the change of tem- 
)erature when the two solutions are mixed, or by the decrease 
n electrical conductivity. The reaction, however, may not go to 
completion. For example, when barium sulphate, a compound 






10 


QUALITATIVE ANALYSIS 



extremely insoluble in water, is mixed with a strong solution 


sodium carbonate, the following double decomposition ta] 


place: 


£a£0 4 +Na.+ C0 3 — <=± £aC0 3 +Na>+ S0 4 —. 


That is to say, the reaction is reversible, the substances under¬ 
going a forward and backward reaction until the opposing ten¬ 
dencies in the solution reach a condition of equilibrium where the 
quantity of each of the substances BaSC> 4 , BaC(> 3 , 2 Na + , CO 3 — 
and SO4 remain constant, although the molecules and ions may 
continue to react. Under what conditions, then, will a reaction go 
to completion? In a broad sense a reaction goes to completion 1 
when one of the resulting substances is removed as rapidly as it is 
formed in the solution. This is the case when a gas is formed, or 
an undissociated molecule such as a very weak acid or base; or, by 
the union of H + and OH - ions of an acid and base, water 
being formed, or, by the formation of a difficultly soluble salt, 
a precipitate being thrown out of solution . 1 In all cases the ions 
react and not the molecules. 

The following examples illustrate each of the above con¬ 
ditions : 

Gas formed: 


Zn+ + +H 2 + S0 4 —->Zn+ + S0 4 —+H 2 T . 


Undissociated molecule: 

Fe+ + + C1 3 -+3K+ CNS - —►3 K + Cl~+Fe(CNS) 3 j . 

Water formed: 

Na+ OH-+H+ N0 3 -—>Na+ N0 3 ~+I7 2 0|. 

Precipitate formed: 

Ba++ Cl 2 “ +K 2 + S0 4 ——*2(K+Cl-)+£aS0 4 j. 

Advantage is taken of such reactions in the detection and sepa¬ 
ration of substances in analytical chemistry. 

1 The terms are only relative. We have ^earned that even water dis¬ 
sociates slightly. No compound is absolutely insoluble. 






INTRODUCTION 


It 


Mass Action. —The . Law of Mass Action may be stated as 
follows: The speed of the chemical action between two substances is 
proportional to the molar concentrations in the solution. 

This important law is worthy of consideration. The following 
concrete cases will make it more clear. When a simple com¬ 
pound such as sodium chloride is dissolved in water, it ionizes 
into the cations Na + and the anions Cl - . Concentration of these 
ions causes a reverse action to take place, resulting in the formation 
of the undissociated molecules NaCl. When the solution reaches 
the point of saturation, a further concentration causes precipita¬ 
tion of the salt. According to the Law of Mass Action, the speed 
at which this action takes place is dependent upon the concentra¬ 
tion of the reacting substances Na and Cl. The law may be 
[Na+] [Cl 


expressed by the formula 


NaCl 


= K, that is to say, the 


product of the ionic concentrations divided by the concentration 
of the undissociated molecules is constant. (Temperature remain¬ 
ing constant.) 

A good example of the reaction between two compounds to 
illustrate the law is the reversible reaction 


BaS04+Na2C0 3 <—- BaCOs-f-Na.SCb. 

Let a, b, c, d represent concentration of the reacting substances 
in the order given in the equation. Let k and k f represent the 
constants depending upon the tendency of the substances to 
combine, and S and S' the speed of the reactions, and K the equi¬ 
librium constant. Then from the Law of Mass Action we have 
S = abk, and S' = cdk'. But since equilibrium has been reached, 
the speed of the reaction in both directions is the same, so that 
S and S' may be eliminated; then abk = cdk', or 

— = —. Since —=K, therefore —r=K. 
ab k f k' ab 

From the above it can be seen that by increasing either c or d 






12 


QUALITATIVE ANALYSIS 


more, ab would have to form to restore equilibrium, and th( 
reaction would reverse. The reaction would go forward bj 
increasing a or b. Advantage is taken of this law when an excess 
of sodium carbonate is added to barium sulphate when the con¬ 
version of the latter to a carbonate is desired. The same thing 
could be accomplished by removing one of the resulting con¬ 
stituents. 

Repression of Ionization—The Common Ion Effect.—From 

the Mass Law we can readily see that ionization may be repressed 
by adding to a solution a salt having a common ion with that oi 
the solute. This may be shown in an interesting way by adding 
concentrated hydrochloric acid or a strong solution of sodium 
hydroxide to a saturated solution of sodium chloride. In eithei 
case a copious precipitate of NaCl takes place. In the first case 
we have increased the concentration of the anions Cl - , in the 
second case that of the cations Na + . Reverse reactions take 
place to restore equilibrium, forming undissociated molecules 
NaCl. But since the solution is already saturated with the salt 
precipitation immediately takes place. 

Another interesting example is the repression of the ionizatior 
of the weak base ammonium hydroxide by addition of ammonium 
chloride, a salt with the common ion NELL Advantage is 
taken of this fact in preventing precipitation of Mg (OH) 2 b } 
NH4OH in both qualitative and quantitative analysis—ammonium 
hydroxide added to a water-soluble magnesium salt will pre¬ 
cipitate Mg (OH) 2; if however, sufficient NH4CI is present, mag¬ 
nesium hydroxide is not precipitated, since the addition of NH4C" 
increases the NH4 ions in the solution, and, by the common ior 
effect, represses the hydroxyl ions of the base NH4OH, so thal 
there are insufficient hydroyl ions for the solubility product 0 
Mg(OH)2 to be exceeded; magnesium therefore remains ir 
solution. 

Solubility Product.—Salts do not have to be extremely soluble 
in order to ionize; even a difficultly soluble salt such as silve: 




INTRODUCTION 


13 


chloride dissolves to’ a slight extent in pure water, and dissociates 
forming the ions Ag+ and Cl“. 

a n-A + Pi- [Free ions Ag + ] [Cl~] 

^ ® ’ 6 Undissociated molecules AgCl 

The product of the concentration of the ions Ag + XCl“ is 
known as the solubility product. These two values jointly 
determine the extent of the solubility of the substance. 

The following principles apply to precipitation and solution of 
substances in terms of their solubility product. 

Exceeding the solubility product, hy addition of a compound 
with a common ion will decrease the solubility of the precipitate. 
For example, the addition of HC1 to the water containing the 
precipitate AgCl will render it less soluble. Hence, in precipitat¬ 
ing silver chloride an excess of hydrochloric acid is used when it is 
desired to remove silver from a solution; for the same reason an 
excess of silver nitrate is added to a solution when it is desired to 
remove the chlorine ions. 

Precipitation of an electrolyte takes place when its solubility 
product is exceeded. For example, when ammonium oxalate is added 
in excess to a solution of calcium chloride, a precipitate of calcium 
oxalate takes place. The solubility product of the calcium oxalate 
is easily exceeded, the anions of the ammonium oxalate in excess 
furnishing the conditions necessary. Calcium oxalate in solution 
ionizes into Ca ++ C 2 0 4 —. This may be expressed the equation: 

[Ca++] [C 2 0 4 —1 
CaC 2 0 4 

It is evident that increased concentration of the ions C2O4 
necessitates for formation of more of the unionized CaC 2 04 in 
the presence of (NH 4 ) 2 + C 2 04 — in excess. The solution soon 
becomes saturated, and calcium oxalate precipitates. 

Solution of a precipitate takes place on the addition of a substance 
that decreases the product of ionic concentrations below the solubility 




14 


QUALITATIVE ANALYSIS 


product of that compound. For example, if hydrochloric acid is 
added to the precipitate of calcium oxalate, the salt dissolves. 
This is accounted for by the fact that HC 1 is highly ionized, 
whereas H2C2O4 dissociates but feebly, and scarcely at all in the 
presence of free H • anions, e.g. in the presence of an acid such as 
HC 1 . Hence the anions of calcium oxalate combine with the 
hydrogen cations of HC 1 , forming the weak acid H2C2O4. The 
removal of the C2O4 — anions from solution reduces the product 
of the concentrations of Ca ++ and C2H4 , ions in solution below 
the solubility product of CaC 2 C >4 causing the precipitate of cal¬ 
cium oxalate to dissolve to establish equilibrium. The reaction 
continues until all of the precipitate goes into solution. 

Unionized CaC 2 04 —»ions Ca ++ C 2 O 4 . 

Ca++ Cj0 4 + 2 (H+ Cl“) ->Ca++Cl a -+i 7 2 C 2 04 . 

Silver chloride dissolves in ammonia water on account of the 
formation of the complex cation Ag(NH 3 ) 2 + causing the removal 
of the Ag cation from Ag + Cl - , thus decreasing the solubility 
product. 

In general, an insoluble salt of a given acid will interact and 
dissolve when treated with a solution containing another acid that 
is more highly ionized, provided the salt is not one of extreme 
insolubility. CaC 204 dissolves in HC1, but not in HC2H3O2, 
since oxalic acid is weaker than hydrochloric acid but stronger than 
acetic acid. On the other hand, BaS 04 is insoluble in HC1, since 
it is an extremely insoluble salt. 

Electromotive or Potential Series.—The paragraph on elec¬ 
trolysis dealt with the separation of the elements of an electrolyte 
by means of electromotive force. The tendency of 
metals, however, is to pass from the free element to 
the ionic condition. This tendency varies according 
to the element. 

The following list on the left gives the metals 
arranged in the order of the most active to the least 


Potassium 

Sodium 

Lithium 

Barium 

Strontium 

Calcium 




INTRODUCTION 


15 


Magnesium 

Aluminum 

Manganese 

Zinc 

Cadmium 

Chromium 

Iron 

Cobalt 

Tin 

Nickel 

Lead 

Hydrogen 

Antimony 

Bismuth 

Arsenic 

Copper 

Mercury 

Silver 

Palladium 

Platinum 

Gold 


active of the series. The ones preceding have a 
greater tendency to ionize than the ones succeeding, 
and will displace the latter in their combinations, 
when added to solutions of their salts, liberating the 
positive elements in metallic form. 

Zinc, for example, placed in a solution of silver 
nitrate, will cause silver to crystallize out, e.g. 

Zn+ 2 AgN 03 —> Ag2-HZn(N03)2. 

Only the metals above hydrogen will displace it from 
the ionic state; that is to say, these only are attacked 
by acids with liberation of hydrogen. For example 
iron reacts with hydrochloric acid, bismuth does not. 
The elements below II, however, are attacked by cer¬ 
tain oxidizing agents. HNO3, for example, forms 
oxides with the metals Cu, Sb, Bi, Hg, and Ag, which 
oxides in turn are readily acted on by the acid, form¬ 
ing soluble ionized salts and undissociated water. 
The noble metals Pd, Pt, and Au are attacked by 
powerful oxidizing agents such as chlorine liberated in the pres¬ 
ence of a catalytic agent. 



16 


QUALITATIVE ANALYSIS 


LABORATORY DIRECTIONS 


The student of qualitative analysis should be familiar with the 
laboratory processes involved in the study of general inorganic 
chemistry. Believing this to be the case, the author has inten¬ 
tionally omitted detailed directions of such processes; however, 
he deems it advisable to mention, in a cursory manner, some of the 
important operations involved in the laboratory. 

Qualitative analysis involves two kinds of tests, (a) dry reac¬ 
tions, and (6) wet reactions. 

Dry Reactions.—These tests are applied to the solid, dry sub¬ 
stance before its ions are tested in solution. A compound may 
frequently be detected by this method. 

Heating the Substance.—The dry material is placed in a hard 
glass test tube and heated directly in the Bunsen flame. Sub- | 
limation may take place or the mate- 1 
rial may decompose, changing in 
color, or giving off gas which can be | 
recognized by certain characteristics. I 
Ammonium chloride heated in a 
test tube will illustrate sublimation. 
Heating mercuric oxide shows a color ! 
change of the solid, together with 
decomposition with the evolution of 
oxygen. 

Blowpipe Tests.—The following 
illustration (Fig. 2) shows the struc¬ 
ture of the flame, a knowledge of 
which is essential in blow-pipe or 
flame oxidation and reduction tests: 

When a reducing flame is required in blowpipe analysis, hold 
the blowpipe just on the edge of the hot zone, and blow gently. 
The tip of the flame will be slightly luminous, due to the presence 
of unburned carbon. See Fig. 3. 



Fig. 1.—Bunsen Burner. 












INTRODUCTION 


17 


Oxidizing Flame is obtained by inserting the blowpipe nozzle 
into the center of the flame and blowing as before. The flame 

/N--Higher oxidizing flame. Excess of oxygen but 

/ \ not as hot as tne lower oxidizing flame 

/ \ —Zone of complete combustion 

Luminous point of reducing flame 
Reducing flame 
Hottest portion of the fjame 
Lower oxidizing flame. Excess of oxygen 
CJnburned gas 
Low temperature 


Fig. 2.—Structure of the Flame. 




should now be colorless, due to complete combustion of the carbon. 
The tip of the flftme will now be an oxidizing flame. See Fig. 4. 













18 


QUALITATIVE ANALYSIS 


The material to be tested is placed in a small hollow on a piece 
of charcoal. Reduction to the metallic state occurs when the 
reducing flame is blown steadily on the compound. 

Metals may be oxidized by the non-luminous tip of the oxidiz¬ 
ing flame. 

A special tip that flattens the flame is used for blowpipe 
tests. 

Flame Oxidation and Reduction without the Blowpipe.—Oxi¬ 
dation and reduction flame tests can be made directly in the Bunsen 
flame without the use of the blowpipe, a process generally more 
successful in the hands of the beginner. 

The pulverized material is thoroughly mixed with sodium 
carbonate (fused), and a minute portion picked up on the end 
of a splinter of wood specially prepared for the test. The material 
is inserted into the reducing flame for a few moments, then lowered 
into the cool zone of unburned gas until it cools slightly, then 
removed, scraped off, and examined. A blowpipe test should 
be made, using a crystal of copper sulphate of silver nitrate. 

Thick wooden matches may be prepared for the reduction 
test as follows: Boil the matches for half an hour in a strong 
solution of two parts of sodium carbonate to one part of alum. 
Remove and dry. Now coat each match (head removed) two- 
thirds of its length with sodium carbonate by rubbing it into the 
melted salt. Now hold the coated match in the flame, revolving 
the splint rapidly. Repeat the operation until the match is 
thoroughly coated. Char it slightly, and place aside for use. 

Film Tests.—These tests may be best made by condensing the 
volatile product on the cold surface of a porcelain evaporating dish 
filled with cold water. Reduction tests are made by dipping a 
thread of asbestos into the substance to be reduced, and inserting 
it into the reducing flame, and at the same time holding the dish 
immediately over the tip of the reducing flame (Fig. 2). A 
reduced metal will leave a metallic stain on the porcelain. This 
deposit should be examined and tested. For example, arsenous 








INTRODUCTION 


19 


Dxide is reduced to black metallic arsenic. The spot is readily 
soluble in a drop of bleaching-powder solution. 

Oxidation tests are made by simply raising the porcelain dish 
until the tip of the oxidizing flame impinges against it. A fresh 
sample of the material is held in the reducing flame on a thread of 
isbestos. The reduced metal is reoxidized as it passes up through 
;he oxidizing flame, and deposits as an oxide film on the porcelain 
dish. As the test takes but a few seconds, the dish remains cold, 
50 that the volatile products readily condense upon it. 

Flame Color Tests. —One end of a fine platinum wire two or 
Free inches long is fused into a glass rod of convenient length. 
The test is made by dipping the wire into the material to be tested 
ind inserting it into the flame. Since chlorides are volatilized 
eadily, the material is best moistened with strong HC1 before 
naking the test. The color of the flame frequently leads to the 
letection of a metal, especially a member of the alkaline earths 
>r the alkalies. The examination of the flame by means of the 
pectroscope is of especial importance, since each metal has its 
iwn characteristic spectra. 

The platinum wire should be thoroughly cleaned by repeatedly 
lipping it into concentrated hydrochloric acid and holding it in 
he Bunsen flame, or better still, in the flame of a blast lamp until 
iO color is imparted to the flame. 

Borax Bead Tests. —A platinum wire, similar to the one men- 
ioned under Flame Color Tests, is used in the Borax Bead Tests. 
The free end of the platinum wire is coiled in a small loop, through 
yhich an ordinary match will barely pass. The loop is inserted 
nto the flame until white hot, then plunged into powdered borax, 
t is now held in the hottest part of the flame. The borax swells 
,nd melts into a crystalline bead. The material examined is picked 
ip on the bead and tested, first in the reducing flame, then in the 
oxidizing flame. The color imparted to the bead may lead to 
mportant conclusions as to the substance. The student is advised 
o make tests with salts of nickel, cobalt, iron, and copper. 




20 


QUALITATIVE ANALYSIS 


Wet Reactions.—These tests are made with substances in 
solution. The greater portion of our course in qualitative analy¬ 
sis deals with wet reactions. The following hints will be of 
value. 

Filtration.—A fine precipitate will clog the filter paper and 
render the process of filtration slow and tedious; therefore it is 


i e i 



a 

Test Tube. 



b 

Erlenmeyer Flask. 


Fig. 5. 



c 


Wash Bottle. 


necessary to have the particles as large as possible. This is accom 
plished by adding the precipitating reagent to the hot solution o 
the salt and allowing the mixture to cool slowly, whereupon th< 
small particles dissolve and larger crystals form. Before filtering 
it is well to heat the solution almost to boiling, as hot water filter; 
more rapidly than cold water. The paper should be moistene( 
before it is used, as the first portion of the filtrate is apt to b( 
turbid if poured on a dry filter. The filter is made as follows 












INTRODUCTION 


21 


h e circular filter paper is folded in half and again folded 
/ith one edge overlapping, as shown in Fig. 8. The corner of 
he short fold is torn off so that the 
>aper fits the funnel snugly at the base 
f the cone, avoiding a crease, which 
rtnild permit air being drawn in. Air 
ucked in on the edge of the paper 
etards filtration. 

Suction.—The filter pump is used to 
dvantage in filtration. To prevent the 
liter paper from tearing, a platinum 
one is placed in the funnel before in¬ 
erting the filter. A small Buchner 
unnel may be used in place of the ex- Fig. 6.—Method of Filtering, 
•ensive platinum cone. 





Platinum 

Cone. 


Fig. 7 . 




Gooch Crucible. 


Where a filter pump is not available, filtration is hastened by 
ingthening the funnel tube, thus increasing the hydrostatic 






























22 


QUALITATIVE ANALYSIS 


pressure due to the column of water that forms in the tube during 

filtration. , . 

Asbestos Filter.—When strong acids are used m dissolving s 
precipitate, and it is necessary to filter the solution without dilu¬ 
tion, an asbestos filter should be used. This filter is made bj 
pouring clean, long-fibered asbestos, suspended 
in distilled water, over a Witt plate or a wad 
of glass wool placed in a funnel connected to 
a filter flask and suction pump and drawing 
down hard. The filter should not be more 




Stem oj 
Funnel 


Folding of Filter. 


Filtering Funnel. 


Fig. 8. 


than one-tenth of an inch in thickness. A Gooch crucible or 
Buchner funnel may be used. 

(Impurities of the asbestos are removed by HNO 3 , HC1 ai 
distilled water used in turn.) 

Evaporation.—A porcelain dish or casserole should be us* 



Porcelain Dish. 



Fig. 9. 























INTRODUCTION 


23 


when it is necessary to evaporate a solution to small bulk, and 
especially when the solution is evaporated to dryness. Glass 
is apt to crack when the liquid is driven off from the solid material. 

Operations which cause the evolution of disagreeable gases 
should be conducted in the hood. 

Cleaning of Apparatus— The importance of using clean appara¬ 
tus cannot be over-emphasized. The glassware should never be 
put away dirty. A few minutes should 
be given at the close of the laboratory 
period to “cleaning up.” The glass 
should be cleaned with chromic acid 
cleaning mixture, followed by tap water 
i and then distilled water. Before putting 
t away it should be wiped dry with a 
clean towel, or tissue paper. Test tubes 
nay be conveniently placed in a rack 


Frn. 10.—Test-tube Rack. Fig. 11.--Test-tube Brush. 

made for this purpose. See Fig. 10. The tubes are cleaned out 
by means of a brush. 

Recording Results— The student should keep a record of all 
analysis of “unknown,” e.g., the solids or solutions given to him for 
analysis by the members of the laboratory staff. Neatness in 























24 


QUALITATIVE ANALYSIS 


keeping such records should be insisted upon. The following form 
has been found convenient: 


Substance and precedure 

Result 

Indication 

Conclusion 

Orig. sol.+HCl 

Ppt. 1 -f hot water 

Ppt. 2 + NH 4 OH 

Sol. 2+K 2 Cr0 4 
Sol.3+HNO, 

White ppt. 1 
Ppt. 2+sol. 2 
Black ppt. 3 
-f" sol. 3 
Yellow ppt. 
White ppt. 

HC1 group 

AgCl, HgCl+PbCl 2 
Hg+HgNH 2 Cl and 
Ag(NH 3 ) 2 + Cl- 
PbCr0 4 

AgCl 

HC1 group present 

Hg present 

Pb present 

Ag present 

Example of Report of an Unknown 


Group 


Members Found to be Present 

HC1 


Ag, Hg, Pb 

H 2 S (a) 


Pb 


(&) 


None 


(NH 4 ) 2 S (a) 

None 



(b) 

None 



(NH 4 ) 2 CO 3 
Soluble 
Acid ions 


Ba 

Na, K 
N0 3 , C0 3 

Name of the analyst. 
Place and date. 


Suggestions. —The descriptive sections afford a ready reference 
for those desiring a brief outline of properties and occurrence o 
the elements. A list of the more common compounds will be 
found in Part V. A comparison of the solubilities of these com 
pounds will be found helpful in the study of reactions. 

The student should be required to write out the reaction; 
involved in the preliminary tests of the elements. These reaction; 
should enable him to understand the processes involved. 

As classroom work is essential to the course, the pupil shoulc 
be prepared to recite upon the topics suggested at the close 0 
each group, and be able to give the reasons for the steps involve 
in the separation of the elements. 














INTRODUCTION 


25 


CLASSROOM REVIEW 

1 . Define the following, giving examples illustrating the terms: 
Residue, filtrate, precipitate, chemical reaction, ion, oxidation, 
reduction, neutralization, decantation, clear solution.. 

2 . What is meant by hydrolysis? 

3. What is a complex ion? 

4. When is a reaction said to be reversible? Give an example 
of a reversible reaction. 

5. What is meant by mass action? 

6 . State laws governing the solubility of a compound in a 
given solution, giving examples illustrating the laws. 

7. Give an example showing the use that can be made of the 
knowledge of the potential series of elements. 

8 . Outline the structure of a Bunsen flame, showing the 
zones of the flame, the hottest and coolest portions, the oxidizing 
and reducing zones. 

9. Why is it important to keep the glassware clean? 

10. Why is it an advantage to have the precipitate coarsely 
granular rather than fine, or gelatinous, a washing of the precipi¬ 
tate being desired? 

11. How are bead tests made? Film tests? Flame tests? 

12 . What is an amphoteric electrolyte? 






PART II 


THE METALS 

The metals are the bases that form the positive ions of salts in 
solution. These elements are recognized by characteristic com¬ 
binations with certain acid radicals forming difficultly soluble salts, 
and, in a few cases, by colors produced by the fomation of com¬ 
plex cations. 

The metals are classed under five divisions on account of their 
deportment towards certain general reagents. These groups are 
first isolated and, by subsequent processes of elimination, the 
individual ions are recognized. It is thought best to designate 
these groups by the names of the precipitating reagents, and in 
case of subdivisions by terms expressing a common property oi 
the members. 

A number of the metals occur so rarely that they are omitted 
in elementary courses of qualitative analysis. These are included 
below in brackets. The groups are characterized as follows: 

Hydrogen Chloride Group 

Metals whose ions unite with Cl - to form insoluble chlorides 
Silver, Ag+; Mercury, Hg + ; Lead, Pb ++ ; (Tungsten, W; Thal¬ 
lium, Tl; Tantalum, Ta; Molybdenum, Mo; Tellurium, Te). 

Hydrogen Sulphide Group 

Metals whose ions unite with S to form sulphides tha - 
are insoluble in dilute mineral acids. 

(a) Insoluble H 2 S Subgroup: Sulphides insoluble in (NH^Sx 
Mercury, Hg ++ ; Lead, Pb + + ; Bismuth, Bi + + + ; Copper, Cu ++ 

26 








THE METALS 


27 


Cadmium, Cd + + ; (Rhodium, Rh; Palladium, Pd; Osmium, Os; 
tuthenium, Ru). 

(6) Soluble H 2 S Subgroup: Sulphides soluble in (NHU^Sx. 
Arsenic, As +++ , As +++++ ; Antimony, Sb +++ ; Sb +++++ , Tin, 
5 n ++ , Sn + + + + ; Gold, Au + , Au +++ ; Platinum, Pt+ + , Pt ++++ ; 
Iridium, Ir; Molybdenum, Mo; Tellurium, Te; Selenium, Se). 

Ammonium Sulphide Group 1 

Metals whose ions unite with S to form sulphides that 
ire insoluble in NH4OH in the presence of NH4CI. 

(a) Precipitated as hydrates by NH4OH: Iron, Fe +++ ; Alumi- 
mm, Al +++ ; Chromium, Cr +++ ; (Glucinum, Gl; Cerium, Ce; 
Neodymium, Nd; Praseodymium, Pr; Erbium, Er; Lanthanum, 
jSl; Columbium, Cb; Scandium, Sc; Tantalum, Ta; Titanium, Ti; 
Thorium, Th; Yttrium, Yt; Ytterbium, Yb; Zirconium, Zr). 

( 1 b ) Precipitated as sulphides by (NLLO 2 S: Nickel, Ni ++ ; 
Cobalt, Co ++ ; Zinc, Zn + + ; Manganese, Mn + + ; Iron, Fe ++ ; 
Uranium, U; Indium, In; Thallium, Tl; Gallium, Ga; Vana- 
lium, V). 


Ammonium Carbonate Group 

Metals whose ions unite with CC>3 - ~ to form carbonates 
nsoluble in NH4OH in the presence of NH4CI; Calcium, Ca ++ ; 
Strontium, Sr + + ; Barium, Ba ++ . 

Soluble Basic Group 

Metals whose cations do not readily combine with anions to 
orm insoluble salts and are not precipitated by a common reagent: 
Magnesium, Mg ++ ; Ammonium, NH 4 + ; Sodium, Na + ; Potas¬ 
sium, K + ; (Lithium, Li; Caesium, Cs; Rubidium, Rb.) 

1 . 1 The valences are given for the forms in which the elements are iso- 
ated. For the other valences, see pages 81-108. 




28 


QUALITATIVE ANALYSIS 


LABORATORY EXPERIMENTS 

When a chemist analyzes a substance, he first examines the 
solid by spreading it out upon white glazed paper and notes 
whether it is homogeneous or heterogeneous. If the substance 
is a mixture, he endeavors to find out the number of different 
substances present, and is frequently able to detect substances 
by the color and crystalline form. Following the physical exami¬ 
nation he gives a small portion of the material preliminary tests., 
which often prove valuable in subsequent work and may prove 
conclusively the presence of certain elements. He is now ready tc 
examine the substance systematically. He first dissolves the 
material and then, by a process of precipitation and solution 
separates the ions into the general groups, and later isolates and 
identifies the individual members. He now makes tests for the 
acid radicals, his knowledge of the presence of certain metak 
being of assistance in this analysis. 

CHARACTERISTIC REACTIONS OF REPRESENTATIVE MEMBERS 
OF THE GROUPS 

As we have seen, the elements are grouped together ir 
several general groups. Our study in this section will dea 
with a characteristic member of each general division to shov 
why this grouping has been adopted in analytical chemistry. 

Hydrogen Chloride Group.—Silver will serve as a characteristii 
member of this group. 

1. Pour 2 or 3 cc. of silver nitrate solution in a beaker am 
add about 10 cc. of water; now add dilute HC1 as long as a pre 
cipitate will form. Stir the solution and allow to settle. Add * 
few more drops of HC1 to see that the reagent has been addec 
in excess. Filter by decantation, pouring the last of the solutioi 
with the precipitate on the filter. Wash once by pouring a few cc 
of distilled water on the residue. The precipitate is silver chloride 

Reaction.—AgN0 3 -}-HCl= j AgCl+HNOa. 



THE METALS 


29 


2 . Test the filtrate with the following group reagents in the 
ollowing order. Pass in H 2 S. Does a precipitate form? 

3. Make alkaline with NH 4 OH and add (NH 4 ) 2 S. Does 
i precipitate form? 

4. Now boil to remove sulphur, and Piter if sulphur separates 
>ut. To the alkaline solution add (NII 4 ) 2 C0 3 . Evidently all 
)f the silver is removed by the first reagent. 

Hydrogen Sulphide Group.—Copper is a characteristic mem- 
3 er of the general group. Separation of the subdivisions of this 
;roup will be taken up under the study of the general group later. 

5. Take 2-3 cc. of Cu(N0 3 ) 2 solution, dilute with water, and 
idd HC1. Does a precipitate form? 

6 . Now pass in H 2 S as long as a precipitate forms. It is well 
o heat the solution, though not essential in this case. Filter 
md test the filtrate to see that all of the copper is removed by 
Dassing in more H 2 S. 

Reaction.—Cu(N0 3 ) 2 +H 2 S = | CuS+2HN0 3 . 

7. If the work is carried on properly, the reagents, which 

are used to precipitate the following groups, will have no effect 
upon the filtrate from CuS, obtained in experiment 6 . Try these— 
[a) Add NH 4 OH and (NH 4 ) 2 S. (b) Add (NH 4 ) 2 C0 3 . 

Ammonium Sulphide Group.—Iron is a characteristic member 
pf the general group. 

8 . Take 2-3 cc. of Fe(N0 3 ) 3 solution, dilute with water, and 
I idd HC1, then pass in H 2 S. 

9. Boil to expel H 2 S and filter if sulphur separates out, 
idd HNO3 to oxidize the iron, and heat to boiling. 

10. Make alkaline with NH 4 OH. The reddish brown pre¬ 
cipitate that forms is Fe(OH) 3 . 

Reaction.—Fe(N0 3 ) 3 +3NH 4 0H—»Fe(0H) 3 +3NH 4 N0 3 . 

11. Add (NH 4 ) 2 S. The precipitate turns black, due to the 
ormation of FeS. 

Reaction.—2Fe(OH) 3 +3(NH 4 ) 2 S = j 2FeS+S+6NH 4 OII. 





30 


QUALITATIVE ANALYSIS 


If sufficient reagent has been added, all of the iron will be 
completely precipitated. 

Ammonium Carbonate Group.—Calcium is a characteristic 

member of this group. 

12. Take 2-3 cc. of Ca(NOs )2 solution and dilute with a few 
cc. of water. Note the following facts: The reagents HC1, H 2 S, 
NH4OH, and (NH 4 ) 2 S produce no effect upon the ionized salt. 

13. Add (NH4) 2CO3. A precipitate is immediately thrown 
down. The white substance is CaCOs- 

Reaction.—Ca(N0 3 )2 + (NH 4 ) 2 C 03 = i CaC0 3 +2NH 4 N0 3 . 

If the solution is made acid by addition of HC1, the precipitate 
dissolves. 1 

The Soluble Basic Group.—Sodium is a characteristic member 
of this group. Use 2-3 cc. of NaNC >3 solution. Convince your¬ 
self that the metal is not precipitated by any of the reagents thus 
far used. 


SEPARATION OF THE GROUPS 

14. Make a mixture of the solutions of the metals studied 
above, e.g. 2 cc. of each of the following: AgNC>3, Cu(N03)2 ; 
Fe(N03)3, Ca(NC> 3 ) 2 , and NaNC>3. Add dilute HC 1 until nc 
further precipitate forms and filter. Silver is removed as a 
chloride. 

15. Heat the filtrate nearly to boiling, and add H2S. Coppei 
separates as black CuS. Test the filtrate to insure the complete 
removal of this group, refiltering if a precipitate forms. 

16. Expel H2S by boiling and add NH4OH; observe that the 
iron separates out. This will be in the form of green ferrous 
hydroxide. 

17. Oxidize by the addition of HNO3, boil, and again mak< 
alkaline with NH4OH. The precipitate will now be red Fe(OH)3 

18. Add (NH 4 ) 2 S. Black FeS is formed, and iron is com 
pletely removed. 









THE METALS 


31 


19. Boil the filtrate, and filter if a precipitate or residue 
eparates out. Add NH4OH if the solution is not alkaline, and 
hen add (NEL^COs. White CaC (>3 separates out and the 
titrate contains the sodium. 

20. Evaporate to dryness to expel the ammonium salts, but 
lo not heat to redness. This should be carried on in the hood 
a a porcelain dish. Test the sodium by the flame test. The 
lame is colored bright yellow by the metal. If possible, examine 
/ith a spectroscope. Note the brilliant yellow line. 


Outline Scheme for Separation of the Groups 

To the cold solution add dilute HC1 in excess. Filter. 


Precipitate.—AgCl, HgCl, PbCl 2 . Filtrate.—Heat to boiling, and pass 

in H 2 S as long as a precipitate con- 


| Inues to form. (Test filtrate by passing in more H 2 S.) Filter. 


Precipitate.—(a) HgS, PbS, Bi 2 S 3 , CdS, CuS. 
b) As 2 S 3 , As 2 S 5 , Sb 2 S 3 , Sb 2 S 5 , SnS, SnS 2 , etc. 


Filtrate.—Boil to expel 
H 2 S, and filter if sulphur 
separates. Add HN0 3 , 
nd boil, then make alkaline with NH 4 OH. Iron, aluminum, and chromium 
fill precipitate as hydroxides. Now add (NH 4 ) 2 S and filter. 


Precipitate.—FeS, Al(OH) 3 Cr(OH) 3 , CoS, 
TiS, MnS, ZnS. 

Filtrate.—Boil to small bulk 
and filter to remove sulphur. 
To the filtrate add NH 4 OH 

nd (NH 4 ) 2 C0 3 , and filter. 


Precipitate.—CaC 03 , BaC0 3 , SrC0 3 . 

Solution—Mg ++ , Na+, K+, 
NH 4 + , Cs + acid radicals, etc. 





















32 


QUALITATIVE ANALYSIS 


NOTES AND PRECAUTIONS ON THE SEPARATION OF 
THE GROUPS 

Preparation for the Work—Read thoughtfully the procedure and notes 
before attenpting an analysis. Time spent in the study of the methods 
will be amply repaid by quicker and more accurate results in the laboratory. 

Reagents.—Be sure that the reagents are properly labeled and free from 
impurities. For example, commercial hydrochloric acid would never do for 
qualitative work. 

Stoppers should never be placed on the desk, as they will not only soil 
the desk, but take up contaminating material which will thus find its way 
into the reagent. To prevent stoppers of KOH and NaOH reagent bottles 
from sticking, clean the stoppers, wipe dry, and coat with paraffin. 

Beakers and flasks should be labeled in order to keep track of the work. 
Confusion will be thus saved when running several tests. A careful record 
of the work must be kept as you proceed. 

Precipitates.—Until your results are passed upon, save the precipitates 
to verify your work. 

Decantation will hasten washing of a precipitate, as the solid is apt tc 
clog the filter. Filtering solutions hot, whenever it is possible, is advisable 
since it hastens the work. 

Filter paper should fit the funnel snugly, and not extend above its rim 
It should be moistened with water before being used for filtering the solution 

Funnels should have an angle of 60°, with a narrow stem about five inche: 
in length. The hydrostatic pressure of the column of water in the sten 
hastens filtration. 

Washing the precipitate with small portions of water and allowing th< 
precipitate to drain before adding more wash water should be observed. 

Filtrates should be tested with the group reagent to insure the complet 
precipitation of the group. 

To prevent splashing, have the stem of the funnel touch the side of th 
beaker or receiving vessel. This precaution is absolutely necessary in quanti 
tative analysis, and should be followed now, as it will prevent careless wor 
later. 

Evaporating the solution for tests of the sodium and potassium salts in th 
soluble group should be carried on in the hood, as the volatile ammoniur 
compounds are disagreeable. 

Quantity of the reagents and of the solutions tested should be n 
more than is necessary. The skill of a chemist is determined by his sue 
cess in detecting minute quantities of substances. Much time is saved i 
filtering, and a smaller quantity of the reagent is required for precipitatioi 




HYDROGEN CHLORIDE GROUP 

Silver Group , Group 1 , Hydrochloric Acid Group 
DESCRIPTIVE 

Common Metals.—Lead, Mercury (-ous), Silver. 

Rarer Metals.—Molybdenum, Tantalum, Tellurium, Thallium, Tungsten. 

leneral Characteristics . 

The metals of this group belong to separate families in the 
)eriodic arrangement. The common elements—silver, mercury, 
tnd lead—are grouped together quantitatively on account of their 
omparatively insoluble chlorides, whereas the chlorides of the 
>ther metals are soluble in water or dilute acids. The sulphides 
>f this group are also insoluble in dilute acids. 

T ndividual Characteristics. 

LEAD 

*b, at.wt. 207.2; sp.gr. 11.34; m.p. 327° C.; b.p. 1526° C.; oxides, PbO, Pb0 2 , 

Pb 3 0 4 . 

The soft, bluish-gray metal is easily cut with a knife. When freshly 
ut the metal is bright, but soon tarnishes in moist air, due to surface oxida- 
ion. Lead may be easily melted in the Bunsen flame (m.p. 327° C.) 

Hot, dilute nitric acid is the best solvent of the metal. Lead nitrate 
3 insoluble in concentrated nitric acid, but dissolves readily upon dilution 
dth water. The metal is insoluble in dilute sulphuric acid, but dissolves 
a the hot, concentrated acid. Although not soluble in dilute hydrochloric, 
t dissolves in the hot, concentrated acid, especially in presence of the halo- 
ens chlorine, bromine, and iodine. The metal is soluble in glacial acetic 
cid. 

The following salts are but slightly soluble in water, PbC0 3 , PbCl 2 , 
PbC0 3 • Pb(OH) 2 , PbCr0 4 , Pb 3 (P0 4 ) 2 , PbS0 4 , PbS, PbW0 4 . The compounds 
issolve in hot dilute nitric acid. A list of the more common lead com¬ 
ounds and their solubility, color, and form is given in Part V. 

33 


34 


QUALITATIVE ANALYSIS 


DETECTION 

Hydrochloric acid precipitates lead incompletely from its cold solutioi 
as white PbCl 2 , soluble in hot water, by which means it is separated fron 
mercurous chloride and silver chloride. PbCl 2 forms needle-like crystal 
upon cooling the extract. 

Hydrogen sulphide precipitates black PbS from slightly acid solution! 
along with the other elements of the group. 1 Yellow ammonium sulphide 
sodium sulphide, and the fixed alkalies dissolve out arsenic, antimony am 
tin. The sulphide of lead, together with bismuth, copper, and cadmium 
dissolve in hot dilute nitric acid, leaving mercuric sulphide insoluble. Afte 
addition of sulphuric acid, the extract evaporated to dryness and then h 
S0 3 fumes, expels nitric acid. Upon adding water to the residue am 
boiling with a little additional sulphuric acid, the sulphates of bismuth 
copper and cadmium are dissolved out, lead sulphate remaining as a whit 
residue. 

Confirmatory Test.—Lead may be further confirmed by dissolving tb 
sulphate in ammonium acetate (barium sulphate is very slightly soluble 
and precipitating the yellow chromate, PbCr0 4 , by addition of potassiui 
dichromate solution. 


MERCURY 

Hg, at.wt. 200.6; sp.gr. 13.696; m.p. — 38.9° C.; b.p. 367.33° C.; oxide 

Hg 2 0, HgO 

Mercury is a liquid at ordinary temperatures. It becomes a solid 1 
—38.9° C. The metal remains bright at ordinary temperatures, but ms 
be oxidized by application of heat in presence of oxygen, changing to a ye 
lowish red color. 

Nitric acid is the best solvent for the metal and its amalgams. The oxid 
are insoluble in alkalies. Mercuric oxide is dissolved by acids. Hydr 
chloric acid forms mercurous chloride with the lower oxide, insoluble 
dilute hydrochloric acid. 

Mercury has a valence of one and two, forming two series of salts. T1 
mercurous halogen salts are but slightly soluble in water, whereas the me 
curie halogens are soluble excepting the iodide, which is difficultly solubl 

1 Lead precipitates best from solutions containing 1 cc. of concentrat' 
free hydrochloric acid (sp.gr. 1.19) for each 100 cc. of solution. The si 
phide is appreciably soluble if the acidity is increased to 3 cc. HC1 per 1 
of solution. 





THE METALS 


35 


The sulphides Hg 2 S and HgS are practically insoluble. See list of com¬ 
pounds in Part V. 

DETECTION 

Metallic Mercury is recognized by its physical properties. It is the 
only metal which is a liquid at ordinary temperatures. The element forms 
a convex surface when placed on glass. 

Hydrochloric Acid Test, Hg+.—Mercury in the mercurous form is pre¬ 
cipitated by hydrochloric acid as white mercurous chloride, HgCl. This 
[compound is changed by ammonium hydroxide to the black precipitate of 
metallic mercury and nitrogen dihydrogen mercuric chloride. 

Hydrogen Sulphide Test, Hg + + .—Mercury in the mercuric form is not 
precipitated by hydrochloric acid. The sulphide of the element is thrown 
out from an acid solution as black HgS. The precipitate first appears white, 
(changing to orange-yellow, then brown and finally to black, as the H 2 S gas 
is passed into the solution. The element is distinguished from the other 
members of the group by the insolubility of its sulphide in yellow ammonium 
t sulphide and in dilute nitric acid. 

Mercurous Chloride.—If the mercury sulphide obtained above is dissolved 
in aqua regia, the nitric acid expelled by adding hydrochloric acid and 
ievaporating to dryness, the residue taken up with a little hydrochloric acid, 
diluted with water, and treated with a solution of stannous chloride, a 
| white precipitate of mercurous chloride is first formed, which is further 
[reduced to metallic mercury by an excess of the reagent. 

Metallic copper, iron, zinc, displace mercury from its acid combination 
.in solution, the metal Hg depositing over the surface of the displacing metal. 
See Electromotive Series in Introduction, page 14. 

SILVER 

Ag, at.wt. 107.88; sp.gr. 10.57; m.p. 960.5° C.; b.p. about 1960° C., 

oxides, Ag 2 0, Ag 2 0 2 

Silver is a white, ductile, malleable metal, harder than lead, but easily 
I cut with a knife. It is a good conductor of electricity and heat. The metal 
idoes not tarnish in the air under conditions affecting metallic lead, but in 
presence of H 2 S and moisture the metal turns dark, due to a coating of Ag 2 S. 

Solubility.—Nitric acid, dilute or concentrated, attacks silver rapidly 
I when hot. The presence of a soluble chloride, iodide or bromide in the sol¬ 
vent or substance will retard and may prevent solution. Unless oxidizing 
agents are present, dilute sulphuric acid has practically no action on massive 
silver, but hot, strong acid commences to be an active solvent at a con- 





36 


QUALITATIVE ANALYSIS 


centration of 75 per cent H2SO4. Hydrochloric acid attacks silver super¬ 
ficially. The action of alkaline hydrates or carbonates in solution is inap¬ 
preciable; in a state of fusion, slight. 

The halogen salts of silver are practically insoluble in water. A change 
of color occurs when the salts are exposed to light. The cyanide, ferro and 
ferricyanide and the sulphide are also difficultly soluble in water. Attention 
is called to the list of more common silver compounds given in Part V. 


DETECTION 

A trace of silver in most substances may be detected by furnace assay 
methods. 

A silver salt fused on charcoal with NaaCCb is reduced to metallic silver. 

The wet method of detection of silver most commonly practiced, depends 
upon observation of the properties of the precipitate formed by the addition 
of slight excess of alkaline chloride to a cold nitric or sulphuric acid solution 
of the substance undergoing examination. One-tenth milligram of silvei 
precipitated as silver chloride in a cold 200-cc. acid solution gives a very 
perceptible opalescence to the liquid. 

Silver chloride is white when freshly precipitated, tinted pink when 
palladium is present; in colorless liquids on exposure to light turns brown, 
violet, blue or black. By agitation, heating or long standing the precipitate 
becomes coagulated or granular and in such a state is retained by an ordi¬ 
nary filter. The presence of some forms of organic matter prevents coag¬ 
ulation. 

Silver chloride is dissolved by concentrated hydrochloric acid; raisin* 
the temperature of the acid assists the action. It is dissolved by sodii 
thiosulphate, alkali cyanides, mercuric nitrate, and alkaline chlorides. 

From mercurous chloride, silver chloride, except when constituting 
small proportion of the precipitate, is distinguished by its solubility withou 
decomposition in ammonia. Precipitation from its ammoniacal solutioi 
is accomplished by acidifying. 

It is distinguished from lead chloride by its flocculated appearance 
PbCh is granular or appears as needle-like crystals. AgCl is practicall; 
insoluble in hot water in presence of a little HC1, PbCl 2 dissolves. 

Silver Thiocyanate.—Silver, in a cold solution containing free nitric aci 
only a small amount of colored salts, and no mercury, may be detected thro 
the formation of a white precipitate, similar in appearance to silver chlori 
by addition of a slight excess of an alkaline thiocyanate. 











THE METALS 


37 


LABORATORY EXERCISES 

Chemical Reactions 
LEAD 

1. To a few cc. of a solution of a lead salt [Pb(N 03)2 or 
* 13 ( 0211302 ) 2 ] add HC1—The white precipitate is PbCl 2 . 

Reaction.—Pb(N0 3 ) 2 +2HCl = | PbCl 2 +2HN0 3 . 

2. Wash once by decantation with cold water, then add more 
i/ater and boil; the precipitate slowly dissolves. Look up the 
olubility of PbCl 2 in list of compounds in Part V. 

3. Decant the clear liquid through a filter and divide in two 
•ortions. Allow one to cool; PbCL crystallizes out in fine needles. 

4 . To another cooled portion add a few drops of H2SO4. The 
hite precipitate is PbSC>4. 

Reaction.—PbCl 2 +H 2 S0 4 = I PbS0 4 +2HCl. 

5. If PbSC >4 is dissolved in NH4C2H3O2 and a solution of 
! [ 2 CrC >4 or K2O2O7 is added, a yellow precipitate, PbCr0 4 will 
e thrown out of the solution. 

6 . PbS 0 4 is soluble in HN 0 3 , KOH, NH4C2H3O2. PbCr0 4 is 
)luble in KOH, but not in HC2H3O2. Test solubility of lead 
llphate with the reagents stated. 

Pb(C 2 H 3 0 2 ) 2 +K 2 Cr0 4 = i PbCr0 4 +2KC 2 H 3 0 2 . 

MERCURY 

7. Use soluble mercurous salt, HgNOs. Add HC1—the white 
recipitate is HgCl (calomel). 

Reaction.—HgN0 3 +HCl = i HgCl+HN0 3 

8. Wash the precipitate by decantation to remove HC1, then 
oil with water and filter off the clear solution. 



38 


QUALITATIVE ANALYSIS 


9. Test the filtrate for mercury by passing in H 2 S; the presenc 
of mercury is indicated by a black precipitate of HgS+Hg. j 
negative test indicates the insolubility of HgCl in hot water. 

Reaction if Mercury is Present.— 2 HgCl+H 2 S = Hg 2 S+2HCl 

Hg 2 S= i HgS+Hg 

10. Add NH4OH to the HgCl precipitate in a beaker. Th 
precipitate turns black, owing to the formation of mercuri 
ammonium chloride and free mercury. 

Reaction.—2HgCl+2NH 3 = I NH 2 HgCl+Hg+NH 4 Cl 

11. Pour off the ammonia, wash once by decantation and ad< 
aqua regia; the precipitate dissolves, forming the soluble HgCl 
(corrosive sublimate). 

Reaction.—NH 2 -HgCl-f Hg-j-5Cl = T N+2HgCl 2 +2HCl 

12. Boil the solution to expel the excess of aqua regia. Dilut 
with a few cc. of water and add SnCl 2 solution. The precipitat 
is HgCl, white. SnCl 2 in excess gives Hg, gray. 

Reaction.—2HgCl 2 +SnCl 2 = 2 HgCl+SnCl 4 
2HgCl+SnCl 2 = 2 Hg+SnCl 4 

SILVER 

13. Use a solution of AgN 03 . Add HC1—the white curdy pn 
cipitate is AgCl. 

Reaction.—AgN0 3 +HCl = | AgCl+HN0 3 

14. Add water and filter by decantation to remove free HC 
add more water and boil and again filter. 

15. Test the filtrate for silver by passing in H 2 S. Does a pr 
cipitate form? If silver is present a black precipitate will fom 
Or add KI, in presence of silver a yellow precipitate, Agl w 
form. The tests will be negative in absence of silver, which w 
be the case if AgCl has been completely precipitated. 



THE METALS 


39 


16. Add NH4OH to the precipitate placed in a test tube; 
he precipitate dissolves owing to the formation of the soluble 
silver ammonium chloride, Ag(NH3)2Cl. Upon acidifying this 
dear solution with HNO3, silver chloride is precipitated. 

Reactions.— AgCl+2NH 3 = T Ag(NH 3 ) 2 Cl 

Ag(NH 3 ) 2 Cl+2HN0 3 = J AgCl+2NH 4 N0 3 

TABLES OF REACTIONS 

Tests of the elements are given in Part V. The arrangement in the form 
i tables enables the student to make a comparison of the reactions of members 
,f a group with reagents used in their isolation and detection. 

Example. —The first table gives the comparison reactions of the Hydro- 
en Chloride Group. 

Ten tests are given for lead, the solution of lead nitrate being indicated 
t the top of the second column, and the fist of reagents in the first column, 
’’he reagents used are HC1, NH 4 OH, H 2 S, K 2 CrC> 4 , K 4 Fe(CN)c, Na 2 C0 3 , 
JaOH, SnCl 2 , H 2 S0 4 , Zn. 

The resulting reactions are shown in the second column in line with the 
13 agent used. 

The same reagents are applied to the solutions of mercury and silver. 
'he tables may be used for laboratory tests if so desired. 







40 


QUALITATIVE ANALYSIS 


Outline of the Procedure for the Separation of Mercury (Ous) 
Lead and Silver 

From the laboratory tests it is evident that the chlorides 
of the metals, mercury in its lower valence, lead and silver are 
precipitated when a soluble chloride is added to a solution con¬ 
taining these elements. By filtering off the precipitates a separa¬ 
tion from other substances that may be in solution is effected. 
The fact that lead chloride dissolves in hot water while the 
chlorides of silver and mercury (ous) do not, makes it possible to 
separate lead from silver and mercury by boiling the mixed 
chlorides in water and filtering. Lead may be recognized in 
the filtrate by adding dilute sulphuric acid, which forms the 
water-insoluble, white PbSCL, or by adding a soluble chromate, 
which precipitates yellow PbCrCb. If lead is present in suf¬ 
ficient quantity, cooling the extract causes the formation of 
needle-like crystals of PbCL- A separation of silver chloride 
from mercurous chloride is accomplished by treating the mix¬ 
ture with ammonia; the silver chloride dissolves with formatior 

I 

of the water-soluble compound Ag(NH 3 ) 2 Cl and is removed bj 
filtration. Silver is recognized by neutralizing the NH4OH anc 
the NH3 of the silver compound, with HNO3. Mercuroui 
chloride is converted to a black substance. NH^HgCl+Hj 
by the ammonia. Confirmation of mercury is accomplishe( 
by dissolving the substance in aqua regia and treating th< 
HgCl 2 , thus formed, with SnCl 2 , whereupon a white precipitat* 
of HgCl, or gray precipitate containing metallic mercury, prove 
the presence of this element. 


\\ 




THE METALS 41 


Procedure of Separation of the Hydrogen Chloride Group 

l _ 


To about 15 cc. of the cold neutral or acid solution of the original dissolved 
substance add 5 cc. HC1 (1.12). Shake and allow to settle. Filter, washing 
he precipitate by decantation with a small quantity of water, 5 to 10 cc. at a 
ime, adding the washing to the filtrate until it is about three times the original 
volume. 

I. 

Precipitate.—White—contains AgCl, 
IgCl, PbCl 2 . 

Add 15 to 20 cc. of hot water and 
>our repeatedly through filter while 
iot; heat if necessary. Wash the residu 
nsure complete solution of PbCl 2 . 

II. 

Filtrate.—Contains ions of the 
following groups. Set aside for 
subsequent analysis. 

e with additional fresh hot water to 

Residue.—AgCl, 

IgCl. 

Pour 10-15 cc. 

TH 4 OH repeatedly 

hrough filter paper, 

ontaining the resi¬ 
due to insure the 

olution of AgCl. 

V. 

Filtrate.—Pb+ + Cl 2 - (if allowed to cool, needle-like 

crystals will be deposited = PbCl 2 ). 

Divide the hot solution in two portions. 

(a) To the 
smaller portion 
add K 2 Cr 2 0 7 or 
K 2 Cr0 4 . A yellow 
ppt. is PbCr0 4 , 
soluble in NaOH. 

( b ) To the larger cooled portion 
add one-fifth of its volume of H 2 S0 4 
cone. Cool, shake, and allow to stand 

5 min. 

Ppt. PbS0 4 , white, solu¬ 
ble in NaOH, NH 4 C 2 H 3 0 2 
solutions. Reprecipi- 

L ated from the latter by 
HC 2 H 3 0 2 +K 2 Cr0 4 as yel¬ 
low PbCr0 4 . 

Fil. 
Tl. pptd. 
by KI as 
yellow 
TIL 


Residue.—HgNH 2 Cl+Hg, black. 

Confirm as follows: tear off a portion of the 
liter containing the residue, drop into a test tube, 
tnd add a few drops of aqua regia. Warm, 
lilute, and filter. 

The filtrate contains Hg + + Cl 2 ~. Boil the solu¬ 
tion to destroy the excess of aqua regia and add 
MC\ 2 ; a white ppt. of HgCl or a gray ppt. 
agCl+Hg proves the presence of mercury. 

Filtrate.—Ag(NH 3 ) 2 +Cl- 
Acidify with dil. HNO 3 — 
a white ppt. is AgCl. 

AgCl fused on charcoal 
with Na 2 C0 3 in reducing 
flame yields metallic silver. 


The rarer metals are precipitated by HC1 as follows: W as H 2 W0 4 *H 2 0, 
vhite; T1 as T1C1 3 , white; Ta as HTa0 3 , white; Mo as H 2 Mo0 4 , white; Te as 
WTeOa, white, Ta, Tl, and Te classified also in later groups. 

KClOa-fHCl may be used in place of aqua regia. Boil off Cl. 




























42 


QUALITATIVE ANALYSIS 


Notes on the Separation of the Hydrogen Chloride Group 

I. The addition of HC1 to alkaline solutions may precipitate members 
of other groups, for example, arsenic (yellow), antimony (orange), and tin 
(brown). All such precipitates must be dissolved before undertaking further 
analysis. (See Preparation of Solutions, Part IV.) 

White BiOCl and SbOCl may precipitate, but the addition of HC1 will 
cause these to dissolve. In concentrated solutions NaCl, BaClj, etc., may be 
precipitated. These dissolve on dilution. 

Precautions.—Sufficient IIC1 should be added to precipitate all the silver, 
mercury, and lead. It is well to allow the precipitate to settle and add a 
drop or so of the reagent to see whether the precipitation is complete or to 
test the filtrate for members of the group. This precaution should be observed 
in the analysis of the subsequent groups, as insufficient group reagents will 
cause considerable difficulty later and erroneous interpretations, owing tc 
metals passing into groups to which they do not belong. A large excess oi 
HC1 should be avoided on account of the solubility of the chlorides in HC1 | 
PbCl 2 is slightly soluble in cold water, causing it to pass into the the sub¬ 
sequent group, where it precipitates as PbS. 

The precipitate is washed to insure the removal of other salts that may b( 
carried down by the chlorides. 

If silver has not been completely removed it may be detected in the filtrat* 
by passing in H 2 S 

AgN 03 +H 2 S = 2HN0 3 + J, Ag 2 S black. 

The sulphide is insoluble in alkali hydroxides and sulphides, but dissolve ■ 
in hot dilute nitric acid. 


3Ag 2 S+8HN03 = 6AgN0,+2N0+4H 2 0+3S. 

II. Lead chloride dissolves slowly, hence the precipitate is repeated!; 
washed with hot water. 

III. Turbidity, resulting upon the addition of NH 4 OH to the residu 
left after the removal of lead, is generally caused by the precipitation of th 
white basic salt of lead Pb(OH)Cl, due to the incomplete removal of lea 
through insufficient washing of the combined chlorides with hot water. Th 
presence of lead chloride, however, does not interfere with the tests for mercur 
as the lead salt dissolves in HN0 3 . 

In the test for lead either method is sufficient proof of its presence. 

IV. The change of color of the white residue to black is a characterise 
reaction of mercurous chloride. The confirmatory test is made in case c 
doubt where the discoloration is not decided. 







THE METALS 


43 




The precipitation of AgCl from its ammonium solution by dilute nitric 
acid is a sufficient confirmation of its presence. 

Metallic mercury reduces AgCl to metallic silver: 

Hg -f 2 AgCl = HgCl 2 +2 Ag 

The silver thus reduced does not dissolve in NH 4 OH but remains with the 
mercury precipitate. If the quantity of mercury is large and that of silver 
relatively small, all of the silver will remain with the mercury precipitate 
so that the ammonia extract will fail to show the presence of silver. In 
case a large black residue remains after the ammonia treatment, dissolve 
the residue in aqua regia, dilute with water, filter and test the residue on the 
filter for silver, by extracting with ammonia and acidfying the extract with 
nitric acid as directed. 






44 


QUALITATIVE ANALYSIS 


CLASSROOM REVIEW 

1. Turn to the Comparative Tables, Part V, and study the reaction! 
indicated under Hydrogen Chloride Group. From the insolubilities devis< j 
a plan other than the one given, for the separation of the members of this 1 
group. 

2. Name the metals of the Hydrogen Chloride Group. Why are the} 
classed together? 

3. Does the group precipitant throw out all the members of the grouf 
completely? 

4. Does the absence of a precipitate prove the absence of all the metals j 
of this group? 

5. Does the precipitate always indicate the presence of the silver group? 

6. What would be the result if HC1 were added to a hot solution con-1 
taining the members of this group? 

7. If AgCl were not all dissolved by the NH 4 OH treatment where woulc 
it appear later? How would its presence be proved in the mercury residue' 
Why does mercury prevent the complete extraction of AgCl by NH 4 OH? 

8. Why should the aqua regia be destroyed before testing for mercurj 
with SnCl 2 ? 

9. If the ammonia solution of silver is turbid, what is the cause? 

10. Explain the reaction of NH 4 OH with AgCl. 

11. Why are precipitates washed? 

12. Account for the facts that lead and mercury appear in the following 
group. 

13. How would you distinguish corrosive sublimate (HgCl 2 ) from calome 
(HgCl)? 

14. If the solution to be tested is alkaline, would acidification with H 2 SO. 
do as well as HN0 3 ? 

15. How would metallic silver be distinguished from metallic lead? 

16. If considerable matter remained, after an attempt to dissolve the 
substance for a qualitative examination, how would you prove that some oi 
the substance had dissolved? 

17. How can you distinguish between the chlorides of lead, mercury 
and silver? 

18. Write the reactions that take place when: (a) HC1 is added tc 
AgNO s . Pb(N0 3 )2, HgNO a . (6) HgCl-faq. reg. (c) NH 4 OH added tc 
AgCl, HgCl, PbCl 2 . (d) PbCl 2 +H 2 S0 4 . (e) PbCla+I^CrO*. 





HYDROGEN SULPHIDE GROUP 

Copper and Tin Groups, Group 2 
DESCRIPTIVE 

Common Metals. — Sulphides insoluble in ( NHi)- 2 Sx —Bismuth, Cadmium. 
Copper, Lead, Mercury. 

Sulphides soluble in ( NHi) 2 S x —Antimony, Arsenic, Tin, Gold, Platinum. 

Rare Metals.— Sulphides, insoluble —Osmium, Palladium, Rhodium, 
Ruthenium. 

Sulphides, soluble —Iridium, Molybdenum, Selenium, Tellurium, Tungsten. 

General Characteristics. 

Tha members of this group, though widely scattered in the 
periodic system of classification, are grouped together qualita¬ 
tively on account of the insolubility of their sulphides in dilute 
acids. They subdivide into two groups—metals whose sulphides 
are insoluble in ammonium sulphide or polysulphide, and metals 
whose sulphides are soluble in these reagents. These subdivisions 
are frequently spoken of as the Copper and Tin Groups; we will 
speak of them as the Insoluble and Soluble H 2 S Subgroups, A 
and B. 

THE INSOLUBLE H 2 S SUBGROUP—A (COPPER GROUP) 

The sulphides of this subgroup are insoluble in yellow ammonium sulphide. 

Individual Characteristics. 

L ea( i—its slight solubility as a chloride causes a small amount to pass 
into this group. The metal has been taken up in the previous group. 

Mercury is bivalent in this group. Its characteristics have already been 
discussed. 

BISMUTH 

Bi, at.wt. 208.0; sp.gr. 9.747; m.p. 271° C.; b.p. 1420° C.; oxides, Bi 2 0 3> Bi 2 0,. 

Bismuth is a reddish white metal. It is exceedingly brittle and easily 
powdered. The element is a poor conductor of heat and electricity. It ha 9 

45 




46 


QUALITATIVE ANALYSIS 


a low melting-point (271° C.) hence can be easily melted in the Bunsen flame. 
The metal possesses the peculiar property of expanding when the molten 
mass solidifies and cools, the expansion taking place after solidification. 
Bismuth is the most diagmagnetic substance known. It occupies an extreme 
place in the thermo-electric series and is used with antimony in the prepara¬ 
tion of delicate thermopiles. 

Nitric acid is the best solvent of bismuth. Although it is soluble in hot 
sulphuric acid, it is only very slightly soluble in the cold acid. The element 
is practically insoluble in hydrochloric acid, but readily dissolves in nitro- 
hydrochloric acid. The hydroxides, oxides, and most of the bismuth salts 
are readily soluble in hydrochloric, nitric, and sulphuric acids. 

The salts of bismuth in solution on dilution, give a white precipitate of 
basic salt, which is insoluble in tartaric acid and blackens with H 2 S (distinction 
from antimony). A list of the more common compounds may be found in 
Part V. 

DETECTION 

General Procedure.—Bismuth is precipitated from its solution, contain¬ 
ing free acid, by H 2 S gas, as a brown sulphide, Bi 2 S 3 . The compound is 
insoluble in ammonium sulphide (separation from arsenic, antimony, and 
tin), but dissolves in hot dilute nitric acid (separation from mercury). The 
nitrate, treated with sulphuric acid and taken to S0 3 fumes, is converted to 
the sulphate and dissolves upon dilution with water (lead remains insoluble 
as PbSCL). Bismuth is precipitated from this solution by addition of 
ammonium hydroxide, white Bi(OH) 3 being formed (copper and cadmium 
dissolve). If this hydroxide is dissolved with hydrochloric acid and then 
diluted with a large volume of water, the white, basic salt of bismuth oxy¬ 
chloride, BiOCl, is precipitated. The compound dissolves if sufficient hydro¬ 
chloric acid is present. It is insoluble in tartaric acid (distinction from 
antimony). 

Reducing Agents.—Formaldehyde in alkaline solution, hypophosphorous 
acid, potassium or sodium stannite, reduce bismuth compounds to the metallic 
state. For example, a hot solution of sodium stannite poured onto the white 
precipitate of Bi(OH) 3 on the filter will give a black stain. The test is very 
delicate and enables the detection of small amounts of the compound. 

3K 2 SnO 2 +2BiCl 3 +6KOH =2Bi -f 3K 2 SnO 3 +6KC1+ 3 H 2 0 

Blowpipe Test.—A compound of bismuth heated on charcoal with a 
powdered mixture of carbon, potassium iodide and sulphur, will give a scarlet 
incrustation on the charcoal. 


THE METALS 


47 


CADMIUM 

Cd, at.wt. 112.4; sp.gr. 8.642; m.p. 320.9° C.; b.p. 778° C.; oxide, CdO 

Cadmium is a bright silvery metal of faint bluish tinge. Like lead it 
produces a metallic streak on paper, but not so readily. The metal is harder 
and more tenacious than tin and is ductile and malleable. Heated to 80° C. 
it becomes brittle and may be powdered in a mortar. It crackles like tin 
when bent on account of its crystalline structure. It has a comparatively 
low melting-point (320.9° C.), when heated in air it burns, evolving brown 
fumes of the oxide. 

Cadmium is slowly soluble in hot, moderately dilute hydrochloric acid 
and in sulphuric acid, much more readily in nitric acid. It is soluble in 
ammonium nitrate. The oxide is readily soluble in acids. 

The salts of cadmium, generally, are but slightly dissociated in solution, 
hence are liable to be incompletely precipitated by reagents. A list of the 
more common salts is given in Part V. 

DETECTION 

General Procedure. —Cadmium is precipitated by hydrogen sulphide 
from an acid solution as yellow cadmium sulphide, CdS. The precipitate is 
insoluble in ammonium sulphide (distinction from arsenic, antimony, and 
tin), but dissolves upon addition of hot nitric acid (separation from mercury). 
Upon addition of sulphuric acid and explusion of nitric by taking the solu¬ 
tion to SO 3 fumes, and dilution with water, cadmium remains in solution 
(lead is precipitated, PbSO<). Bismuth is precipitated by ammonium hydrox¬ 
ide and removed by filtration. Potassium cyanide is added to prevent the 
precipitation of copper sulphide; and hydrogen sulphide is led into the 
solution, whereupon cadmium precipitates as yellow CdS. 

Spectrum. —Cadmium gives a brilliant spectrum of green and blue lines. 

Blowpipe Tests.—Heated on charcoal in the reducing flame, cadmium 
gives a brown incrustation. The residue is volatile in the reducing flame. 


COPPER 

Cu, at.wt. 63.67; sp.gr. 8.89 20 °; m.p. 1083° C. (in air 1066); b.p. 2310° C.; 
oxides Cu 2 0 and CuO 

The reddish (salmon red) ductile and malleable metal is an excellent 
conductor of heat and electricity. It possesses a bright metallic lustre when 
freshly cut but soon tarnishes. It is not acted on by dry air under ordinary 





48 


QUALITATIVE ANALYSIS 


conditions. The basic carbonate, verdigris (CuC 0 3 *Cu( 0 H) 2 ) is formed in 
moist air. Copper heated in the air is coated with black cupric oxide. 

The metal is insoluble in HC1 and in dilute H 2 S0 4 (see Electromotive 
series) but dissolves in concentrated H2SO4, and in dilute HNO 3 . It is pre¬ 
cipitated from solutions of its salts by metals nearer sodium in the electro¬ 
motive series. 

The element has two valences, hence forms two series of salts, cuprous 
and cupric (see list in Part V). The copper ions of the bivalent form are 
blue, the monovalent ions are colorless. 

DETECTION 

General Procedure. —Copper is precipitated in an acid solution by H 2 S 
gas, along with the other members of the hydrogen sulphide group. The 
insolubility of its sulphide in sodium sulphide is a means of separating copper 
from arsenic, antimony, and tin. The sulphide dissolves in nitric acid 
(separation from mercury) along with lead, bismuth, and cadmium. Lead 
is precipitated as PbS0 4 by sulphuric acid, and bismuth is precipitated as 
Bi(OH) 3 , ammonium hydroxide. Copper passes into the filtrate, coloring this 
solution blue. 

Flame Test.—Substances containing copper (sulphides oxidized by 
roasting), when moistened with hydrochloric acid and heated on a platinum 
wire in the flame, give a blue color in the reducing flame and a green tinge to 
the oxidizing flame. 

Wet Tests.—Nitric acid dissolves the metal or the oxides (sulphides should 
be roasted), forming a green or bluish-green solution. Ammonium hydroxide 
added to this solution will precipitate a pale blue compound, which dissolves 
in excess with the formation of a blue solution. (Nickel also gives a blue 
color.) 

Hydrogen sulphide, H 2 S, passed into an acid solution containing copper, 
precipitates a brownish-black sulphide, CuS. (Distinction from nickel.) 

Copper is displaced from its solution by zinc, cadmium, tin, aluminum, lead, 
bismuth, iron, cobalt, nickel, and magnesium . If a strip of iron is placed 
in a solution of copper, neutral or slightly acid, it will be coated over with 
metallic copper. (Delicacy 1 part Cu per 120,000 of -solution.) 

The greenish-blue cupric salts in acid solution are reduced to the colorless 
cuprous compounds by metallic copper and by stannous chloride and by 
arsenious acid, grape sugar, sulphurous acid in alkaline solutions. 

Potassium Ferrocyanide precipitates reddish brown cupric ferrocyanide, 
insoluble in dilute acids, soluble in NH 4 OH. 1 part Cu may be detected 
in 200,000 parts of water, the solution appearing reddish brown. 


THE METALS 


49 


THE SOLUBLE H 2 S SUBGROUP— B (TIN GROUP) 

The sulphides of this subgroup are soluble in yellow ammonium sulphide. 

individual Charateristics. 


ANTIMONY 

Sbj at.wt. 120.2; sp.gr. 6.62; m.p. 620° C.; 1440° C.; oxides, Sb 2 0 3 , 

Sb 2 0 4 , Sb 2 0 5 . 

Antimony as it ordinarily occurs is a lustrous, bluish white metal with 
janular or coarsely laminated structure according as it is quickly or slowly 
ooled. It is brittle and may be readily powdered in a mortar. It is a poor 
onductor of heat and electricity. The metal has two amorphous forms, 
»ne form is soluble in CS 2 , the other is an unstable variety which easily 
hanges to the crystalline form by heat or by being scratched or struck. The 
netal is not affected by air at ordinary temperatures, but burns at red heat 
rith formation of white Sb 2 0 3 . Like bismuth antimony expands on solidi- 
ication. It is oxidized by nitric acid, dilute HN0 3 producing principally 
>b 2 0 3 and concentrated HN0 3 , the pentoxide Sb 2 0 5 . Antimony combines 
iirectly with the halogens with evolution of light and heat. It unites with 
aetals and forms a number of useful alloys. Antimony generally increases 
he fusibility, brittleness and hardness of the metals with which it is com- 
>ined, and imparts the property of expanding on solidfication—an important 
actor for castings. 

Metallic antimony is practically insoluble in cold dilute hydrochloric, 
dtric or sulphuric acid and the oxides, Sb 2 0 3 or Sb 2 05 , are precipitated in 
trong nitric acid. The element, however, is readily soluble in hydrochloric 
.cid containing an oxidizing agent, such as nitric acid, potassium chlorate, 
hlorine, bromine, etc. The oxides of antimony are soluble in hydrochloric 
.cid and the caustic alkalies. 

Most of the salts in solution precipitate basic salts when diluted with 
rater. Tartaric acid prevents precipitation (see Detection). A list of 
.ntimony compounds is given in Part V. 

DETECTION 

Hydrogen Sulphide precipitates the orange-colored sulphide of antimony 
rom fairly strong hydrochloric acid solutions (1 :4) in which several mem- 
>ers of the group remain dissolved. Arsenic is also precipitated. The latter 
nay be removed by boiling the solution containing the trichloride, AsClj 
>eing volatile. 


50 


QUALITATIVE ANALYSIS 


General Procedure.—If antimony is already present as a sulphide, 
together with other elements of the hydrogen sulphide group, it may be 
dissolved out by treating the precipitate with sodium hydroxide or potassium 
hydroxide or sodium sulphide or ammonium polysulphide. Antimony sul¬ 
phide is precipitated upon acidifying the filtrate. Arsenic and tin will also be 
precipitated with antimony if they are present in the original precipitate. 
Should a separation be necessary, the precipitate is dissolved with hot con¬ 
centrated hydrochloric acid, with the addition of crystals of potassium chlorate, 
from time to time, until the sulphides dissolve. The solution is placed in a 
Marsh apparatus, pure zinc added and the evolved gases passed into a neutral 
solution of silver nitrate. The black precipitate of silver antimonide and 
metallic silver are filtered off, washed free of arsenous acid, and the antimonide 
dissolved in strong hydrochloric acid (silver remains insoluble). The orange- 
colored antimony sulphide may now be precipitated by diluting the solution 
with water and passing in H 3 S gas to saturation. See also page 78. 

Minerals which contain antimony, when heated alone or with 3 to 4 parts 
of fusion mixture (K 2 C0 3 and Na 2 C0 3 ), on charcoal, yield dense white fumes, 
a portion of the oxide remaining as a white incrustation on the charcoal. A 
drop of ammonium sulphide placed upon this sublimate gives a deep orange 
stain. 

Hydrolysis.—Most of the inorganic antimony salts are decomposed by 
water, forming insoluble basic salts, which in turn break down to the oxide of 
antimony and free acid. An excess of tartaric acid prevents this precipitation. 
(Distinction from bismuth.) 

Distinction between Antimonous and Antimonic Salts. 

Chromates form with antimonous salts green chromic salts and antimonic 
salts. 

Potassium Iodide reduces antimonic salts, free iodine being liberated. 

Traces of Antimony.—Nascent hydrogen liberated by the action of zinc 
and hydrochloric or sulphuric acid reacts upon antimony compounds with the 
formation of stibine. This gas produces a black stain on mercuric chloride or 
silver nitrate paper. 

Comparison of the Marsh Tests for Antimony and Arsenic 

Stibine and arsine are formed by the reduction of compounds of the cor¬ 
responding elements by nascent hydrogen; both leave a deposit in the form 
of a black mirror on a cold white surface when the flames of the ignited gases 
impinge against the cold body. The stain of arsenic, however, is soluble 
in a hypochlorite solution, while that of antimony is not. Arsine passed 
through a solution of AgN0 3 will reduce the compound, forming black flakes 


THE METALS 


51 


of metallic silver. Stibine does not reduce silver nitrate, but precipitates 
black silver antimonide. The arsenic mirror, dissolved in a drop of HNO s 
then evaporated to dryness and the residue moistened with a drop of silver 
nitrate, gives a brick-red color. Antimony remains colorless. The spot 
dissolved in ammonium sulphide and evaporated to dryness yields a bright 
yellow residue. Antimony residue is orange-red. If arsine is conducted 
through a hard glass tube with a constriction, and this portion of the tube is 
heated, an arsenic mirror forms in advance of the flame. Stibine decomposes, 
depositing antimony immediately above the flame, since antimony is less 
7olatile. 


As 4 at.wt.74.96- 


ARSENIC 

cryst. 6.73 

amorp. s P‘£ r ' 4.72 m ' p * 
Oxides, AsjOj, As 2 O s 


860 subl. 664 e 

... b * p ‘ <360 c 


Arsenic is a brittle steel gray, crystalline metal. It is a good conductor 
of electricity, and is odorless and tasteless. It is volatile at temperatures 
above 100°, and is vaporized rapidly at a dull red heat. The vapor is yellow 
and has the odor of garlic. When heated in air arsenic burns with a bluish 
flame, forming arsenous oxide, As 2 0 3 . It combines in powdered form with 
chlorine, forming AsC 1 3 . With heat it combines withBr, I, and S. Arsenic 
is a constituent of many alloys. 

The metal dissolved in dilute HNOs forms arsenous acid, in concentrated 
HN0 3 arsenic acid. Arsenic occurs in nature in crystalline masses. 

Solubility.—The oxide, As 2 0 3 , is not readily acted upon by dilute acids— 
hydrochloric or sulphuric. The compound is soluble, however, in alkaline 

[ hydroxides and carbonates. Nitric acid oxidizes As 2 O a to the higher oxide, 
As 2 0 5 , which is soluble in water. The sulphides As 2 S 3 and As 2 S 5 are prac¬ 
tically insoluble in hydrochloric or sulphuric acids, but are dissolved by the 
: axed alkalies and alkali sulphides. All arsenites, with the exception of the 
ilkali arsenites, require acids to effect solution. 


DETECTION 

Hydrogen sulphide precipitates the yellow sulphide of arsenic, As 2 S 3 , when 
passed into its solution made strongly acid with hydrochloric acid. If the 
solution contains more than 25 per cent hydrochloric acid (sp.gr. 1.126) the 
j other members of the hydrogen sulphide group do not interfere, as they are 
aot precipitated from strong acid solutions by hydrogen sulphide. Arsenic 
sulphide is soluble in alkaline carbonates. (Antimony sulphide, Sb 3 S», 
reddish yellow, is insoluble in alkaline carbonates.) 










52 


QUALITATIVE ANALYSIS 


(c± 


Tube containing sensitized 
mercuric chloride paper 
4mm bore. 


T" T Rubber stopper. 


Volatility of the chloride, AsC 1 3 , is a means of separation and distinctioi 
of arsenic. The compound is distilled from a concentrated hydrochloric acic 

solution, assisted by a stream of HCl gas 
which separates it from other elements 
Arsenic must be in the trivalent form. 

Blowpipe—The oxide or sulphide 
mixed with Na a CO s and placed on char 
coal heated by the blowpipe gives a filn 
which is volatile and has a garlic odor. 

Open Tube Test.—Arsenic mixed witl 
charcoal and heated in an open tube vola 
tilizes and forms a film of AS 2 O 3 on th< 
cool part of the tube. 

Flame Test.—Pale azure blue. 
Ammonium molybdate solution heate< 
to 50°-G0° with arsenic compounds give 
a crystalline yellow precipitate—ammo 
nium arsenomolybdate. A few drops 0 
nitric acid aid the reaction. The solu 
tion must be concentrated. Add a fe^ 
drops of the arsenic compound to a tes 
tube half full of ammonium molybdat 
containing nitric acid. 

Distinction between Arsenates an 
Arsenites.—Magnesia mixture precipitate 
white MgNH 4 As 04 , when added to ammc 

M Rubber sto er niacal solutions containing arsenates, bu 

it produces no precipitate with arsenites. 

Red silver arsenate and yellow silve 
arsenite are precipitated from neutral soli 
tions by ammoniacal silver nitrate. A 
arsenate gives a yellow precipitate wit 
ammonium molybdate solution. 


/V, Tube containing glass wool 
■ moistened with lead acetate 


solution. 


Rubber stopper. 


Dry lead acetate paper to 
absorb traces of H 2 S. 


;5feiC£SOl; 

^^5fc-cHE 


.0000 OOO o 
5 0 0 0 0 0 0 00 
r O OOO 0000 
00000000 


4 ounce bottle with 
solution containing 


agjjj sample + H a S0 4 (1-4^ 


E^ESE ordil. HCl. 


Traces of Arsenic 


Zinc shot. 


The Gutzeit Test.—The reaction d< 
pends upon the principle that arsine 
formed when arsenic compounds are heate 
in a test tube with pure zinc and a caust: 
alkali or an acid. Filter paper moistened with mercuric chloride held in tl 
fumes of arsine will be turned yellow, deepening to a brown or black. 


Fig. 13.—Modified Gutzeit 
Apparatus. 


















THE METALS 


53 


Modified Gutzeit Method.—An excellent form of apparatus for detecting 
small amounts of arsenic by the Gutzeit method is shown in Fig. 13. By 
this means less than O.OOOOOlg. of arsenic may be detected. The arsenic 
solution containing a small amount of iron is acidified with dilute H 2 SO<-f NaCl, 
the iron and arsenic are reduced with a few drops of strong SnClj solution 
and the mixture poured into a 60 cc. bottle, arsenic-free zinc shot is added 
and the apparatus quickly connected. Arsine produces a black stain on 
the HgCla paper, the length of the stain determining the amount of arsenic 
present. 

H 2 S should be removed by boiling the acid solution and by subsequent 
oxidation with a few drops of KMnC >4 solution. Antimony, if present in 
large amount, will also produce a stain, but ordinarily does not interfere. 

Marsh Test.—This test depends upon the formation of arsine by the reduc¬ 
tion of arsenious or arsenic compounds by nascent hydrogen (H+catalyzer). 



The generator consists of a 250 cc. flat-bottomed flask in which zinc is placed. 
|A thistle tube passes through a two-holed rubber stopper to the bottom of the 
flask. A hard glass tube, drawn out to capillarity at one end, with two 
l jonstrictions near the middle, is connected to the flask by means of a second 
:ube, a tube containing CaCl 2 being inserted. See illustration. The genera¬ 
tor is started by pouring dilute sulphuric acid, which is free from arsenic, 
hrough the thistle tube on to the arsenic-free zinc. A little copper sulphate 
will start the reaction. When the air is expelled, fight the issuing gas; then 
Dour in the solution to be examined through the thistle tube. If arsenic is 
present, the flame will soon be colored a lilac hue by the arsine. If a cold 
i Porcelain evaporating dish is depressed over this flame, a spot of metallic 
irsenic will deposit upon it. This spot will dissolve upon the addition of 




























54 


QUALITATIVE ANALYSIS 


sodium hypochlorite or bleaching powder solutions. Antimony acts verj 
similarly—stibine is formed by the action of nascent hydrogen. The anti¬ 
mony stain is not soluble in sodium hypochlorite. See comparison of the 
Marsh Test for Antimony and Arsneic. 

Gatehouse Test.—Differs only from the above in the materials used foi 
generating hydrogen. This is produced by the action of KOH on Al. 

Fleitmann Test.—KOH or NaOH on Zn used for generating H. 

Bettendorf! Test.—When a mixture of equal parts of cone. HC1 and cone 
SnCl 2 with one part of water is boiled with a few drops of H 3 As0 3 or H 3 AsO< 
the solution darkens, due to the reduction of arsenic to the metallic state. 

Reinsch’s Test.—If a strip of pure copper foil is introduced into a solutior 
containing arsenic acidulated with HC1 and the mixture boiled, the copper wil 
be coated with a gray stain. Antimony and organic matter will do the same 
If the copper foil is removed and dried between folds of filter paper, the foil thei 
rolled into a small coil and dropped into a clean, hard glass tube, then heated 
arsenic will volatilize and collect in the cooler portion of the tube in the forn 
of white octohedral crystals of As 2 0 3 . Organic matter burns away. Anti 
mony deposits in an amorphous form or in acicular crystals. Mercury, whicl 
may also coat the foil, volatilizes and collects in the cooler portion of th 
tube in fine globules of metallic mercury. 

TIN 

Sn, at.wt. 118.7; sp.gr. 6.66; m.p. 232° C.; b.p. 2276° C.; oxides Sn0 2 , SnC 

> 

Tin is a silver white, lustrous, crystalline, soft, malleable metal. It i 
inferior in ductility and tenacity to most of the useful metals, though superio 
to lead. The metal is not oxidized by air at ordinary temperatures. Tii 
forms a part of several important alloys, bronze, pewter, Britannia meta 
It is used for coating over metals to protect them from corrosion. Tin a 
red heat decomposes water. The metal is divalent and tetravalent, henc 
has two series of compounds. A list of the important compounds may b 
found in Part V. 

Tin is soluble in HC1 and in dilute H 2 SO<. It dissolves in aqua regi 
and in hot NaOH and KOH. It is converted to the insoluble metastanni 
acid by HNO*. j 

DETECTION 

General Procedure.—Tin is separated, togetheUwith arsenic, antimonj 
gold and platinum, from the hydrogen sulphide precipitate of the metal 
of the second group, by the action of yellow ammonium sulphide. (Norim 
ammonium sulphide does not readily dissolve the sulphides of tin.) If th 




THE METALS 


55 


immonium sulphide solution is acidulated with hydrochloric acid and the 
icid solution reduced with iron, antimony, arsenic, platinum and gold are 
precipitated in the metallic form. The presence of tin, which is present as 
3 tannous chloride, is indicated by the reducing action of the solution on 
mercuric chloride, a white precipitate of HgCl or a gray precipitate of Hg 
being thrown down. 

The hydrochloric acid solution of the sample is reduced by means of a 
3 mall piece of iron wire and treated with an excess of cold potassium hydroxide. 
The solution is filtered if not clear and an ammoniacal solution of silver nitrate 
added (one part AgN0 3 : 16 parts NH 4 OH). A brown precipitate of metallic 
3 ilver indicates the presence of tin. Antimony, arsenic, platinum and gold 
axe precipitated by the iron, while all of the heavy metals remaining, except 
lead, tin, aluminum, chromium, and zinc, are removed by the treatment 
with potassium hydrate. 

Welch and Weber recommend the following method for detection of tin: 
Ten cc. of concentrated hydrochloric acid are added to the superficially dried 
precipitated sulphides from the ammonium sulphide separation. Arsenic, 
which does not decompose, is filtered off and the filtrate diluted to 70 cc. 
volume, then saturated with H 2 S, and heated to expel excess H 2 S. Five cc. 
of hydrogen peroxide are added, and the mixture heated until the precipitate 
is redissolved. Five to 10 grams of oxalic acid are added and H 2 S passed 
into the hot solution. Antimony separates as a red sulphide. The filtate 
contains the tin. Test lead is added and then mercuric chloride. White or 
grayish precipitate indicates presence of tin. 



56 


QUALITATIVE ANALYSIS 


LABORATORY EXERCISES 
Chemical Reactions 

Insoluble H 2 S Subgroup A (Copper Group) 

The elements will be studied in the order in which their 
isolation is accomplished in the general procedure for separation 
of the members of the group. 

Mercuric mercury, Hg ++ , use a solution of mercuric chloride. 

1. Add 1 cc. HC1 (1.12) and dilute to 10 cc. Warm and pass 
in H 2 S slowly, and note the colors of the precipitates formed. 

Reactions.— 3HgCl 2 +2H 2 S = HgCl 2 -2HgS+4HCl 

HgCl 2 -2HgS+H 2 S= 1 3HgS+2HCl 

2 . Allow to settle, and wash by decantation. Test the solu¬ 
bility of the precipitate in HNO 3 (1 vol. HNO 3 (sp.gr. 1 . 2 ) to 
2 vols. H 2 0). 

3. Test the solubility of HgS in (NH^S* solution . 1 

4. Pour off the acid and wash by decantation and test the solu¬ 
bility in Br water (warm) or in boiling aqua regia. The precipi¬ 
tate dissolves. 

5 . Boil the solution to drive off chlorine. Cool and add SnCl 2 ; 
the white or gray precipitate is HgCl+Hg. 

LEAD 

Use a solution of lead acetate. 

6 . Add 2 cc. HC1, warm and pass in H 2 S, noting the color of the 
precipitate formed (PbS). 

Reaction.— Pb(C 2 H 3 0 2 ) 2 +H 2 S= f PbS+2HC 2 H 3 0 2 . 

7. Allow to settle and wash by decantation. Boil precipitate 
in a casserole with 4 cc. HNO 3 (see above). 

Reaction — 3PbS+8HN0 3 = 3Pb(N0 3 ) 2 + T 2N0+4H 2 0 + 1 3S. 

1 The precipitate HgS dissolves in Na 2 S+NaOH. 









THE METALS 


57 


8. To the solution formed add a few drops of dilute H2SO4; 
the white precipitate is PbSC>4. 

Reaction.—Pb(N0 3 ) 2 +H 2 S0 4 = i PbS0 4 +2HN0 3 . 

Boil until white fumes appear, and dilute. Does the pre¬ 
cipitate seem to have increased? 

9. Dissolve in NH4C2H3O2 and add K^CrCU. Does the pre¬ 
cipitate dissolve when acetic acid is added? Try it. 

Reaction.—Pb (C 2 H 3 0 2 ) 2 +K 2 CrO 4 = j PbCr0 4 +2KC 2 H 3 0 2 . 

10. Take 2 cc. of BaCl 2 and add a few drops of H 2 SO 4 . 

Reaction.—BaCl 2 +H 2 S0 4 = i BaS0 4 +2HCl. 

11. Test the solubility of the white BaSCU in NH4C2H3O2. 

12. Next add a little K 2 Cr 04 to 2 cc. BiCl 3 . Test the solu¬ 
bility of (BiO) 2 CrC >4 in acetic acid. What conclusion do you 
draw from these tests? 


BISMUTH 

Use solution of bismuth chloride. 

13. Add 1 cc. HC1 and dilute to 10 cc. A precipitate of 
BiOCl forms with greater dilution. Try it. 

14. Warm and pass in H 2 S. 

Note the color of Bi2S3. 

Reaction.—2BiCl 3 -f“3H 2 S= J, Bi 2 S 3 +6HCl. 

15. Test the solubility of Bi 2 S 3 in (NH 4 ) 2 S 2 solution. Allow 
to settle, decant and wash once by decantation. Boil the precipi¬ 
tate with 1 cc. of HNO3. 

Reaction.—Bi 2 S 3 +8HN0 3 = J 2Bi(N0 3 ) 3 + T 2N0+4H 2 0+ j 3S. 

16. To the solution of Bi(N 0 3 )3 add a few drops of H 2 S 0 4 . 
Does a precipitate form? 



58 


QUALITATIVE ANALYSIS 


17. Add NH4OH until alkaline; note the color of the precipi¬ 
tate Bi(OH)3. 

Reaction.—Bi(N0 3 ) 3 +3NH 4 0H = | Bi(0H) 3 +3NH 4 N0 3 . 

18. Does the precipitate dissolve in an excess of NH 4 OH? 
Filter and wash once. Dissolve in a few drops of HC1 and pour 
the solution into a second test tube containing 15 to 20 cc, of 
water. Precipitate is BiOCl. 

Reaction.—BiCl 3 +H 2 0= j BiOCl+2HCl. 

19. Filter and add a fresh solution of sodium stannite 
(NaOH+SnC^); the black precipitate is metallic bismuth. 

Reaction.— 

2Bi0Cl+3Na 2 Sn0 2 +2Na0H=3Na 2 Sn0 3 +2NaCl+H 2 0+ i 2Bi 
COPPER 

Use a solution of copper sulphate. 

20. Add 1 cc. HC1 and dilute to 10 cc. Warm and pass in 
H 2 S; note the color of the precipitate, CuS. 

Reaction.—CuS0 4 -l-II 2 S = CuS+H 2 S0 4 . 

21. Test the solubility of CuS in (NELi^S* solution. 

22. Wash by decantation, dissolve in 1 cc. HNO 3 , dilute, and 
add two or three drops of H2SO4. Does a precipitate form? 

23. Boil until white fumes appear, and again dilute. Is there 
a precipitate now? 

Reaction.— 3CuS+8HN0 3 =3Cu(N0 3 ) 2 + 12N0+4II 2 0+ j 3S. 

Cu(N0 3 ) 2 +H 2 S0 4 = CuS0 4 + 12HN0 3 . 

24. Make alkaline with NH 4 OH. Note that the light-blue 
precipitate, formed in a drop or so of ammonia, dissolves in an ex¬ 
cess of that reagent and forms a deep blue solution (Cu(NH 3)4 
ion). 

Reaction.— CuS0 4 +2NH 4 0H = f Cu(0H) 2 + (NH 4 ) 2 S0 4 . 

Cu (OH) 2 +(NH 4 ) 2 SO 4 +2NH 3 = Cu (NH 3 ) 4 S0 4 +2H 2 0. 


THE METALS 


59 


25. Divide the solution into two portions. To one, acidified 
with acetic acid, add K 4 Fe(CN) 6 . Note the color of the precipi¬ 
tate Cu 2 Fe(CN) 6 by pouring on filter paper. 

Reaction.—2CuS0 4 +K 4 Fe(CN) 6 = f Cu 2 Fe(CN);+2K 2 S0 4 . 

26. To the other portion add solid KCN until the color dis¬ 
appears. Now pass in H 2 S. Does a precipitate form? 

Deep blue 

Reaction.—2Cu(NH 3 ) 4 SO 4 +NH 4 OH+10KCN — 

2KsCu(CN) 4 +2K 2 S0 4 +NH 4 CN+NH 4 CNO+7NH s . 

H 2 S does not precipitate CuS when passed into a solution containing 

K 3 Cu(CN) 4 . 


CADMIUM 

27. To a solution of cadmium chloride add 1 cc. HC1, dilute 
to 10 cc., pass in H 2 S; note the color of the precipitate CdS. 

Reaction.—CdS0 4 +H 2 S=CdS+H 2 S0 4 . 

28. Test the solubility of CdS in (NH 4 ) 2 S X solution. 

29. Follow out directions as given in the copper tests. Note 

color of Cd 2 Fe(CN)6- . „ 

30. Does KCN prevent the precipitation of Cdfer 

Reaction.—K 2 Cd(CN) 4 is formed by the action of KCN on the cadmium 
salt. When H 2 S is passed into this solution the reaction takes place as 

follows: K j Cd( CN) «+HjS=CdS+2KCN +2HCN. 





60 


QUALITATIVE ANALYSIS 


Outline of the Procedure for Separation of Members of the 
Hydrogen Sulphide Group. 

For convenience the members of the hydrogen sulphide 
group have been classed under two subdivisions, owing to the 
fact that the sulphides of some are soluble in ammonium poly¬ 
sulphide, while the others are scarcely affected by this reagent. 
Antimony, arsenic and tin sulphides dissolve, while the sulphides 
of bismuth, cadmium, copper, lead and mercury are practically 
insoluble. The separation of these subgroups is accomplished 
by dissolving the soluble sulphides in (NH^Sx solution, filter¬ 
ing, and washing the residue. 

The chemical reactions of the insoluble subgroup have 
shown certain characteristics of the members which enables 
us to separate the four elements from one another. The fact 
that the sulphide of mercury is not dissolved by dilute nitric 
acid makes it possible to isolate HgS from the other sulphides, 
which dissolve. The fact that lead sulphate is practically insoluble 
in dilute sulphuric acid gives a procedure for removing lead from 
bismuth, cadmium and copper, since the sulphates of these 
elements dissolve in dilute sulphuric acid. Bismuth hydroxide 
precipitates when ammonia is added to a solution of bismuth; 
copper and cadmium, on the other hand, form soluble com¬ 
pounds and may be removed by filtration. Copper is recognized i 
in the filtrate, if present in appreciable amount, by the blue : 
color the ammonium compound imparts to the solution. The 
sulphide of cadmium may be precipitated from its solution in 
presence of KCN; the sulphide of copper does not precipitate, 
hence separation may be made. The isolated substances may 
now be confirmed by special tests. 









THE METALS 


61 


Separation of the Hydrogen Sulphide Group 


Heat the filtrate of the HC1 group, or an acid solution containing the 
members of the H 2 S group (1 part HC1 (1.12) to 10 parts of the solution) in an 
Erlenmeyer flask, nearly to boiling. Pass in H 2 S to saturation (5-10 min.) 
keeping the solution hot. Now add one and a half volumes of water and 
again saturate with hydrogen sulphide. Cork the flask, shake, and allow ppt. 
to settle. Filter, and wash the precipitate with hot water. 


1L__ 

Precipitate.—Black—HgS, PbS, CuS. 
Brown—Bi 2 S 3 , SnS. 

Orange—Sb 2 S 3 , Sb 2 S 5 . 

Yellow—CdS, As 2 S 3 , As 2 S 5 , SnS 2 . 
(PtS 2 , Au, Au 2 Si— 3 , Se, Te, Mo, etc.) 


Filtrate.—Ions of the following 
groups together with acid anions. 
Expel H 2 S by boiling and save for 
the analysis of these groups. 


Separation of the Soluble and Insoluble H 2 S Sub-groups, A and B 

Transfer the precipitate to a small dish. Add 5-10 cc. (NH 4 ) 2 S X . (Omit 
he addition of (NH 4 )S X if the analysis does not include the Soluble H 2 S Sub¬ 
group.) Warm the mixture (40°-50°) 10 min. Add 10 cc. H 2 0, filter, and 
vash with hot water. (Add to the wash water 5 per cent of solid NH 4 NO t 
f the precipitate passes through the filter paper.) Hg being absent, NaOH 
nay be used in place of (NH 4 ) 2 S X . 

II. 


Residue Subgroup, A.—HgS, PbS, CuS, 
JdS, Bi 2 S 3 . (PtS 2 ; Au and Au 2 Si_ 3 ; 
lnSi_ 2 ; BaS0 4 .) To the residue in a cas- 
erole add 5-10 c.c. HN0 3 (sp.gr. 1.20) to 2 
ir ols. H 2 0. Heat to boiling and boil for 
everal minutes. Filter and wash the 
precipitate. (Prolonged boiling is apt to 
orm insoluble PbS0 4 , hence should be- 
voided.) 


Filtrate Subgroup, B.— 

(NH 4 ) 3 AsS 4 . 

(NH 4 ) 3 SbS 4 , (NH 4 ) 2 SnS 3 , and 
possibly (NH 4 ) 2 PtS 3 , (NH 4 ) 3 AuS 3 , 
together with rare elements. Save 
for the analysis of the Soluble H 2 S 
Subgroup. 














62 


QUALITATIVE ANALYSIS 


Separation of Members of the Insoluble H 2 S Subgroup A 


IV. 


Residue.—HgS or Hg(N0 3 )2HgS, white. 
(Sn, Au, Pt may be present.) Tear off the 
portion of the filter containing residue, put 
into a casserole, and add 25 cc. of bromine 
water. Warm the covered casserole; stir 
frequently (5-10 min.); boil to expel Br, 
and filter. 1 (KC10 3 added hastens solu¬ 
tion.) To the filtrate add, drop by drop, 
SnCl 2 solution. A white precipitate turning 
gray, with an excess of SnCl 2 , indicates 
Mercury, as HgCl or Hg. 

Filtrate. — Pb + + , Bi + + + , 
Cu ++ , Cd ++ , N0 3 ~. (Barium 
may be present). Add 4 cc. 

H 2 S0 4 (cone.) and evaporate in a 
casserole until white fumes ap¬ 
pear. Cool and pour into 10 cc. 
of cold water, rinsing out the dish, 
Shake, and allow to settle 4 min. 
Filter and wash the precipitate 
with dilute H 2 S0 4 (1.20), and 
finally with water. 

V. 




Precipitate.—PbS0 4 , white (BaS0 4 and (Bi0) 2 S0 4 
may be present.) Dissolve by adding 10 per cent sol. 
NH 4 C 2 H 3 0 2 and pouring steadily through filter. To 
the filtrate add 3 cc. 30 per cent sol. HC 2 H 3 0 2 and a 
few drops of K 2 Cr0 4 . A yellow precipitate proves 
the presence of lead. 

Filtrate. — Bi + + + 
Cu+ + ,Cd + + ,S0 4 — 
Add NH 4 OH unti 
strong odor of ammonk 
persists, on shaking 
Filter and wash th< 

copper and cadmium compounds. 

VI. 



precipitate to remov< 

Precipitate.—Bi(OH) 3 , white. Dissolve by pour¬ 
ing a few cc. HC1 on filter. Evaporate filtrate almost 
to dryness. Add 2 cc. H 2 0 and pour this into beaker 
containing 100 cc. warm water. A white ppt. is 
BiOCl. Filter, wash once, and add on filter a few cc. 
Na 2 SnO 2 . A black stain is bismuth. 

Filtrate.— 

Cu(NH 3 ) 4 ++ blue 

Cd(NH 3 ) 4 ++ , SOU' 

Divide into two poi 
tions, a and b. 





(a) Acidify small portion with acetic 
acid, add 2-3 drops of K 4 Fe(CN) 6 , pour 
on filter; a pink color is due to 
Cu 2 Fe(CN) 6 , proving the presence of 
copper. (Cd 2 Fe(CN)6 is white.) 

( b ) Add solid KCN to destro 
color. Pass in H 2 S. A yellow ppt* i; 
CdS, proving the presence of cac 
mium. 

If the precipitate is dark it may fc 
due to Bi or Pb contamination. 


1 If an insoluble precipitate remains, it is probably Sn0 2 or Sb 2 0 3 . Fus 
with Na 2 C 03 +S and treat sulphides according to procedure in Soluble Hj 
Subgroup. 


















THE METALS 


63 


Optional Method for Precipitation of the H 2 S Group and the Separation 
of its Divisions 

Precipitation.—To a given quantity of the solution add one-ninth of its 
plume of concentrated HC1 and a few drops of HNO 3 . If much acid is 
lready present allowance must be made for it. Transfer the mixture to an 
Irlenmeyer flask and boil to half vol. under the hood. Pass a rapid stream 
f H 2 S through the hot liquid, heating again to boiling once or twice and 
iiaking vigorously. When no more precipitate forms (5 to 10 minutes), 
dd enough water to make the volume a little more than twice the original. 
Continue to pass the gas into the solution until the liquid is cold and no more 
recipitate falls (10 to 15 minutes), filter, and wash. 

Separation of the Divisions.—Transfer the precipitate to a beaker, cover it 
ith concentrated ammonium hydroxide, pass in a rapid stream of H 2 S for 
wo or three minutes, warm gently, shake well, filter, and wash. The sul- 
hides of arsenic, antimony, and tin dissolve promptly, leaving mercury, 
opper, lead, bismuth, and cadmium as a precipitate of sulphides. The 

I ltrate and residue are now treated in the usual way. 

Totes on the Insoluble H 2 S Subgroup A and the Precipitation of the 

General Group 

I. If HNO 3 has been used in dissolving the original substance, and is 
resent to any extent, it should be removed by evaporation with HC1; other¬ 
wise, H 2 S will be oxidized to H 2 0 and free S. The presence of other oxidizing 
lbstances may also liberate free S. 2 FeCl 3 +H 2 S = 2FeCl 2 +2HCl+S. 

Arsenic precipitates best in hot solutions of HC1(1.12) 1 : 10. Further- 
lore, the oxyhlorides of bismuth and antimony do not form. 

Arsenic precipitation takes place slowly; haste will cause loss and subse- 
uent errors. 

Lead, cadmium, and tin are best precipitated in dilute, cold solutions. 

Acidity Test. — The sulphides of this group are precipitated in presence 
f free hydrochloric acid. If the acidity is insufficient precipitation of zinc 
lay occur along with the H 2 S group. On the other hand HC1 present in 
irger amount than recommended in the procedure will prevent complete 
recipitation of members of the H 2 S group. The following acidity test 
r ill be found useful. 

A drop of .solution placed on an indelible lead pencil mark gives a blue 
pot for less than 2 per cent HC1 (1.20); pea green =approx. 5 per cent; 
ellow=over 10 per cent. 






64 


QUALITATIVE ANALYSIS 


Color Indications.—Hot solution: White or yellowish turning to black, du< 
to HgCl 22 HgS —>HgS. Orange is due to Sb 2 S 3 and CdS. Yellow is AS 2 S 
or SnS 2 . All other sulphides of the H 2 S group are black. 

II. When cone. HN0 3 has been used to dissolve the substance, tb 
reagent (NH 4 ) 2 S is better than (NH 4 ) 2 S X for dissolving the SnS 2 and Sb 2 S 
formed, due to the higher valence produced by oxidation, but SnS and Sb 2 S 
do not readily dissolve in the monosulphide, and the polysulphide must b 
used when the elements Sn and Sb have the lower valence. CuS and Hg! 
dissolve to a slight extent in the latter. 

Gold and platinum may be found either with the soluble or insolubl 
subgroups or in both, though they generally pass into the soluble subgroui 
and are tested for there. (Molybdenum colors the solution of (NH 4 ) 2 S X orange 
red. The soluble subgroup may contain the rare elements selenium and tel 
lurium.) The filtrate under II should be boiled free of H 2 S immediate! 
on collecting, if later groups are to be looked for in this solution. 

If the acid has not been removed from the precipitate this will decompos* 
(NH 4 ) 2 Sx with the separation of sulphur. A light-colored residue therefor* 
does not indicate the presence of the insoluble H 2 S Subgroup A. 

III. The sulphides PbS, Bi 2 S 3 , CuS and CdS dissolve readily in HNO 3 0 
the strength indicated in the analysis. Long boiling will act on the HgS. 

A black residue is not to be taken as proof for the presence of mercury 
as it may be sulphur inclosing mechanically small quantities of black sulphides 
Hence this residue should be tested for mercury as directed. 

Note .—Prolonged boiling of the residue III may form PbSO< and basi< 
mercuric sulphate, hence must be avoided. 

IV. Bromine water dissolves the sulphides of mercury, platinum, anc 
gold. Tin remains in the residue if undissolved by the polysulphide. Th< 
addition of the solid, KCIO3, hastens solution, but also dissolves tin. 

Platinum and gold are reduced by SnCl 2 , coloring the solutions reddisl 
brown and purple respectively. Platinum precipitates in a saturated solutioi 
of KC1. Gold forms a purplish black or dark yellow precipitate in the presence 
of Na 2 Cr 0 4 +H 2 C 2 0 4 solution. 

The purpose of boiling the solution until the white fumes of H 2 S0 4 appeal 
is to expel HNO 3 , in which PbS0 4 is soluble. A residue remaining aftei 
treatment of the HgS precipitate with the solvents indicated may be SnO: 
or Sb 2 0 3 . Fuse with Na 2 CC> 3 +S and treat sulphides as members of the 
Soluble H 2 S Group. 

V. Dilute H2SO4 decreases the solubility of PbS0 4 . Bismuth and 
barium may be present, but lead can be separated by means of its solubility 
as a sulphate in ammonium acetate (BaS0 4 insoluble) and the insolubility 
of the chromate salt in acetic acid, whereas the chromate of bismuth is soluble, 



THE METALS 


65 

Again, lead chromate is soluble in KOH, whereas the bismuth salt is in¬ 
soluble. 

VI. A dark color in (6) VI may be due to a trace of lead or bismuth, 
or, possibly, to copper. KCN removes color due to copper. The addition 
of NH4OH will precipitate Fe(OH) 3 , etc., if that group is not completely 
removed in the washing. 

Cd(OH) 2 or Cu(OH) 2 first formed are dissolved in the excess of NH 4 OH, 
forming Cd(NH 3 ) 4 + + and Cu(NH 3 ) 4 + + ; the latter is blue. 

Bi(OH) 3 , white, is precipitated by NH 4 OH, due to hydrolysis. BiOCl is 
less soluble in water at higher temperatures, hence it is better to add the 
BiCl 3 to warm water. 

The presence of an excess of acid will prevent precipitation of bismuth 
due to the reversible reaction BiCl 3 +H 2 0 BiOCl+2HC1. The large 
excess of acid may be neutralized by NH 4 OH added drop by drop, taking 
care to keep the solution slightly acid. 

Sodium stannite, Na 2 Sn0 2 , should be prepared as needed, e.g. 10 per cent 
NaOH is added to 10 per cent SnCl 2 until the precipitate Sn(OH) 2 first formed 
just dissolves. This reagent reduces BiOCl to black metallic Bi, and is a 
very delicate test; small quantities may thus be detected. 

The confirmatory test for bismuth should be made, as lead may appear 
here and be mistaken for bismuth, 

In case Cu 2 Fe(CN) 6 is present only in small amounts, it can best be seen 
by pouring the solution through a filter paper, which will be stained pink 
by the precipitate. Cd 2 Fe(CN) 6 being white does not interfere with the test. 

KCN forms Cu 2 (CN) 2 and Cd(CN) 2 ; the former is stable. KCN first 
forms a yellow precipitate Cu(CN) 2 decomposing into white cuprous cyanide, 
CuCN+cyanogen with an excess of the reagent the precipitate dissolves, 
CuCN+3KCN =K 3 Cu(CN) 4 , colorless solution. H 2 S precipitates CdS, 
yellow, but not CuS, a fact taken advantage of in the separation of copper 
from cadmium. A black precipitate will be obtained should lead or mercury 
be present, as is occasionally the case. Mercury will find its way into this 
solution if the original H 2 S precipitate has not been washed free of HC1, 
since this would yield aqua regia upon addition of HN0 3 and dissolve 
some of the mercury. Lead may be present due to incomplete removal. 
If a black precipitate is obtained, filter and treat the residue with dilute 
H 2 S 04 . PbS0 4 will remain on the filter and CdS0 4 pass into solution. The 
filtrate may now be tested for cadimum by again passing in H 2 S. 

Optional Method.—Professor Hinds gives the following advantages for 
this method of procedure. (1) A definite acid concentration is obtained. 
Upon concentration a twice normal solution of HC1 results, from which arsenic 
readily precipitates. Dilution to twice the original volume gives a half 



66 


QUALITATIVE ANALYSIS 


Stopcock 



Fig. 12. Scott’s Hydrogen Sulphide Generator. 

... 7 ig : 12 shows a convenient form of a generator for obtaining hydrogen sulphide gas 
under pressure. 1 he cylinder A A is constricted, as shown, to support perforated lead 
i k „ G - u P? n , whl c h rests the iron sulphide. The lower end of the chamber is closed to catch 
small particles of FeS that may be carried through the perforations of the disk. Small 
openings admit the acid to A . The level of the acid is below the disk G, so that the acid 
S the 8ulpl “de whenpressure is applied by means of the rubber 
bulb E, the stopcock S being open and S 3 closed. 1 he mercury gauge C is adjusted to blow 
out at a given pressure, to prevent accident, the bulb D preventing the mercury from being 
blown out of the apparatus. A small opening in D allows the escape of the gas When the 
fQ P «f+ r n a o t W 1S T^K OP ? ratl ? n K H 18 conaected t( ? an empty heavy-walled bottle, which in turn 
L ^ i • th g i aSS 4 U Ub fl c .° n . n< : ctl01 } to , the pressure flask in which the precipitation of 
the sid P hide is made, the flask being closed to the outside air. By pressure on the rubber 
bulb E, acid is forced into the chamber A past the disk into the sulphide in A The entire 
system will now be under the pressure indicated by the gauge C The pressure is released 
by opening the stopcock and the flask containing the precipitate th?n disconnected 
The reservoir is designed to hold about two liters of acid, and the cylinder cCntaSing 
the sulphide is of sufficient capacity to hold over one pound of FeS. so that the annaratuf 
will deliver a large quantity of hydrogen sulphide. S ° tPat tPe apparatus 






























































THE METALS 


67 


normal HC1 solution, necessary for the complete precipitation of other mem¬ 
bers of the Group. (2) Oxidation with HN0 3 is to insure tin being present 
in the higher valence so that it may be precipitated as stannic sulphide, 
in which form it is more readily soluble in colorless ammonium sulphide. 
(3) The use of yellow ammonium sulphide is avoided. Copper sulphide 
is only slightly soluble in colorless ammonium sulphide. (4) The time is 
much shortened, 30 to 45 minutes being sufficient for the whole process. 

The concentration of the solution must be above 0.125 N*HC1, to prevent 
the precipitation of the metals of succeeding groups. 




68 


QUALITATIVE ANALYSIS 




Chemical Reactions 

Soluble H 2 S Subgroup, B (Tin Group) 

ARSENIC—As + ++ , As + + + + + 


Since there are two series of salts of arsenic, the. preliminary 
tests should be made with both forms. For arsenous acid use 
AS2O3 dissolved in HC 1 . For arsenic acid use H3ASO4. Com¬ 
parative tests of the two forms may be made on samples side by 
side. 

1. Add 10 cc. of water and 2 cc. HC 1 (1.20). Pass in H2S 
gas and note the fact that the sulphide (AS2S3) from arsenous 
acid precipitates more readily than from arsenic acid. H2S first 
reduces the arsenic acid with separation of sulphur and then 
precipitates AS2S3. By heating the solution, the precipitation ol 
the latter is hastened. 

Reactions.— (a) H 3 As0 4 +H 2 S = J, S+H 2 O+H 3 ASO 3 . 

(6) 2H 3 AsO 3 +3H 2 S = j As 2 S 3 +6H 2 0. 

Note—From strong HC1 solutions and by rapid passage of H 2 S, As 2 S 5 is 
precipitated. Try this: 

Reaction.—2H 3 AsO 4 +5H 2 S= i As 2 S 6 +8II 2 0. 

2. Test the solubility of a portion of each sulphide by pouring 
repeatedly over the separate precipitates 5-10 cc. (NH 4 ) 2 S X . 

Reactions.—(a) As 2 S 5 +3(NH 4 ) 2 S=2(NH 4 ) 3 AsS 4 . 

(6) As 2 S 3 +3(NH 4 ) 2 S x =2(NH 4 ) 3 AsS 4 +S x . 

3 . Unite the two filtrates. Acidify with HC 1 (1.12), and note 
the re-precipitation of the sulphides. Filter and wash the pre¬ 
cipitate. 

Reaction.—2(NH 4 ) 3 AsS 4 +6HC1= j As 2 S 6 + T 3H 2 S+6NH 4 Ci. 

4 . In a porcelain dish (casserole is best) test the solubility of 
a portion of the As 2 S 5 by warming with 5 cc. HC1 (1.20). Now 




THE METALS 


69 


add a few crystals of KCIO3, a crystal at a time, until complete 
solution takes place. Filter. Sulphur will remain on the filter. 

Reactions. —(a) 2 HCI+KCIO 3 =KC14-H 2 0+C102+C1. 

(6) As 2 S 3 +8H 2 0+10Cl = I 3S+10HC1+2H 3 AsO 4 . 

5 . Divide the solution in two portions. Test one portion by 
the Gutzeit test. 

Reaction. — 2 H 3 ASO 4 + 8 H 2 (from Zn+2HC1) = 2AsH 3 -f-8H 2 0. 

6 . Make the other portion alkaline with NH 4 OH, adding a few 
drops in excess, then add magnesia mixture, and stir with a glass 
rod. A white crystalline precipitate forms slowly, MgNH 4 As 04 . 

Reaction.—H 3 As 04 +MgCl 2 +NH 4 Cl= | NH 4 MgAs 04 + 3 HCL 

The reaction takes place with arsenic (As +++++ ) and not 
with arsenous (As +++ ) salts or acids. This may serve as a 
distinction between the two forms. 

7 . Silver nitrate test.— AgN0 3 solution added to a neutral 
solution of an arsenite precipitates Ag 3 As 03 yellow. 

H 3 As0 3 +3AgN0 3 = | Ag 3 As0 3 +3HN0 3 . 

8 . If the arsenic is in a nitric acid solution, heat gently until the 
brown fumes are expelled, dilute with 5 cc. H 2 O, filter, add 5 cc. 
of AgN0 3 solution (if cloudy, filter) to the clear solution, add a 
drop of phenolphthalein, make first alkaline with NH 4 OH and 
then faintly acid with 5 per cent acetic acid solution; a chocolate 
colored precipitate is Ag 3 AsC> 4 . 

ANTIMONY 

9 . Use solutions of SbCl 3 and SbCl 5 in presence of HC1. Try 
the reactions separately on the two solutions. Warm and pass 
in H 2 S. Note the color of the precipitates in each case. 

Reactions.—(a) 2 SbCl 3 +3H 2 S = i Sb 2 S 3 +6HC1. 

(Jb) 2SbCl5+5H 2 S= | Sb2S 6 +10HCl. 



70 


QUALITATIVE ANALYSIS 


10. Dissolve in yellow ammonium sulphide, as in the case 
of arsenic. Re-precipitate by acidifying the filtrate with HC1. 

Reactions.—(a) Sb2S3+3(NH4) 2 S X = 2(NH4) 3 SbS 4 -f-S x . 

( b) 2(NH 4 ) 3 SbS 4 +6HCl = i SbsSe-l- 13HaS+6NH 4 Cl. 

(c) Sb 2 S 3 +3 (NH 4 ) 2 S = 2 (NH 4 ) 3 SbS 3 . 

(d) 2(NH 4 )3SbS 3 +6HCl = Sb 2 S3+ T3H 2 S+6NH 4 C1. 

(e) Sb 2 S 5 +(NH 4 ) 2 S = 2(NH 4 ) 3 SbS 4 . 

11 . Dilute with an equal volume of water, filter, and boil the 
precipitate with HC1 (1.20); tho sulphide dissolves. 

Reactions.— (a) Sb 2 S 3 + 6 HCl = 2 SbCl 3 + T 3H 2 S. 

(6) Sb 2 S 6 -j-6HC1 = 2SbCl 3 + i 2S+ T 3H 2 S. 

Observe that in either case SbCl 3 is formed. 

12. Divide in two portions. Boil to remove some of the acid. 
Pour one portion over a large piece of zinc in contact with platinum 
foil. (Hood if As is present.) The antimony will be reduced 
and form a black deposit on the platinum. 

See Introduction for the Electromotive Series, page 14. 

13. Wash the foil carefully, and place in a solution of hypo¬ 
chlorite. The stain is insoluble; arsenic will dissolve. See 
Marsh test for Arsenic, page 53. 

14. If the stain is dissolved in fuming nitric acid, tartaric acid 
added, the solution warmed to expel the brown fumes, then 
diluted to three volumes with water and a few drops of HC1 added, 
hydrogen sulphide will precipitate orange Sb 2 S 5 . 

15. Dilute the other portion to four volumes and pass in H 2 S; 
an orange precipitate will be thrown out. Write out the reactions. 

16. Dilution of SbCE or SbCE solutions with water, if in¬ 
sufficient HC1 is present, will cause precipitation of the oxychlo¬ 
rides, SbOCl or Sb0 2 Cl. 

Reactions.— SbCl 3 +H 2 0 ?=» | SbOCl-}- 2 HCl. 

SbCl 5 +2H 2 0^± 1 Sb0 2 Cl+4HCl. 


17. The precipitates are soluble in tartaric acid, distinguishing 








THE METALS 


71 


antimony from bismuth, BiOCl being insoluble. Prove these 
statements by qualitative tests. 

TIN 

Use solutions of SnCl 2 and SnCl 4 in presence of HC1. Try 
the reactions separately on the two solutions, noting any difference 
in results. 

18. Warm the solution and pass in H 2 S gas. Note the color 
of the precipitates. 

Reactions.—(a) SnCl 2 +H 2 S = [ SnS+2HCl. 

(b) SnCl 4 +2H 2 S= lSnS 2 +4HCl. 

Note .—SnS and SnS 2 are readily soluble in HC1 (1:1). The solutions 
used should contain not over 2.5 per cent concentrated HC1. 

19. Test the solubility of the sulphides in yellow ammonium 
sulphide and in colorless ammonium sulphide. In the latter 
SnS 2 is soluble, SnS insoluble, hence, the necessity of using 
(NH 4 ) 2 S X in separating this group from the insoluble group. 

Reactions.—(a) SnS + (NH 4 ) 2 S X = (NH 4 ) 2 SnS 3 +Sx. 

(b) SnS 2 +(NH 4 ) 2 S x = (NH 4 ) 2 SnS 3 +S x . 

(c) SnS 2 +(NH 4 ) 2 S = (NH 4 ) 2 SnS 3 . 

20. Add HC1 to the solutions obtained; the sulphide of tin 
SnS 2 is precipitated. 

(NH 4 ) 2 SnS 3 +2HC1 = 1 SnS 2 + t H 2 S+2NH 4 C1. 

21. Stannic Chloride and Stannous Chloride.— To a solution of 
SnCU* add HgCl 2 . Observe that no precipitate forms. Now 
try the same test with a solution of SnCl 2 ; the precipitate is 
HgCl or HgCl+Hg or Hg alone, depending upon the amount 

of reagent used. , .... 

22 To a fresh portion add some pieces of zinc, and acidify 

with HC1. Stannic tin will be reduced and deposit on the zinc. 
See Electromotive Series in Introduction. 





72 


QUALITATIVE ANALYSIS 


23. Scrape off the spongy tin and dissolve in HC1. Now add 
HgCl2; a white or gray precipitate will form. What inference 
do you draw as to the valence of tin obtained in solution in this 
way? 

Write out reactions. 

24. When zinc is placed over platinum and the tin solution 
poured over it, no stain will be deposited on the platinum, but a 
spongy deposit will cover the zinc or separate in the solution. 

25. Observe in the,second solution that H2S does not cause a 
precipitate of SnS when the liquid is strongly acid, but when 
diluted the sulphide will readily precipitate. Advantage is 
taken of the fact that Sb will precipitate in an acid solution of a 
definite strength, as stated above, while Sn will remain in solution. 
See first method of analysis. 

Metastannic acid.—When hot dilute HNO3 acts on metallic 
tin, a white substance is obtained known as metastannic acid, 
SnsOsCOlDio or 5(H 2 Sn03). This is a polymer of stannic 
hydroxide, H^SnOs. The compound is insoluble in acids. The 
compound boiled with concentrated HC 1 forms SngOsCkCOEOs, 
insoluble in HC 1 , but soluble in water. 

26. With a solution of SnsOsC^OEQg make the following tests: 

a. To a portion add HC 1 . The ppt. = Sn505Cl4(0H) 6 -4H 2 0. 

b. To a second portion add NH 4 OH. The ppt. is 5(H2Sn03). 

c. Pass in H 2 S into a third portion. The ppt. = SnS2. 

Stannic compounds are converted into metastannic forms by 
diluting and boiling. Metastannic compounds are converted 
into stannic form by boiling with strong KOH or HC 1 . Stannic 
compounds dissolve in acids. Metastannic compounds are 
insoluble in acid. 





THE METALS 


73 


Gold, Platinum and the Less Common Elements of the Hydrogen 
Sulphide Group 

The properties and characteristic tests of the less common elements 
of the Hydrogen Sulphide group are given in Part VI. 

Tables of Reactions 

The student is referred to the tables given in Part V for a comparative 
study of characteristic reactions of the members of the group. The list of 
reagents used for the tests is given in the first column on the left, the salts 
of the group elements are indicated at the top of the pages and the product 
formed is shown at the intersection of the columns of the reagent and the 
element in question. The reaction tables will be found useful for reference 
and may be used for additional tests for laboratory practice. 






74 


QUALITATIVE ANALYSIS 


Outline of Procedure for Separation of Antimony, 
Arsenic and Tin 

The sulphides of antimony, arsenic and tin dissolve in yellow 
ammonium sulphide, permitting these compounds to be separated 
from bismuth, cadmium, copper, lead and mercury. If the 
solution is acidified the sulphides re-precipitate. Arsenic sulphide 
may be isolated by treating the combined sulphides with strong 
HC1, since this compound does not dissolve, whereas the sulphide 
of antimony and tin pass into solution as chlorides. 

Two methods are given for separation of antimony and tin. 
The first takes advantage of the varying solubility of antimony 
sulphide and tin sulphide in hydrochloric acid of definite strength. 
The second procedure utilizes the principle outlined under Electro¬ 
motive Series in the Introduction. Metallic iron for example 
displaces antimony from its combination as a salt, metallic 
antimony being liberated; tin on the other hand is simply reduced 
from stannic to stannous condition and remains in solution. 
Confirmatory tests may now be made for arsenic, antimony and 
tin on the isolated portions. The directions follow: 

Separation of the Soluble H 2 S Subgroup—B (Tin Group) 
Procedure A 

I. Dilute the yellow ammonium sulphide solution (filtrate of the Insoluble 
H 2 S Subgroup containing (NH 4 ) 3 AsS 4 , (NH 4 ) 3 SbS 4 , (NH 4 ) 2 SnS s and the 
excess (NH 4 ) 2 S X ), with about 25 cc. H 2 0. Add HC1 (sp. gr. 1.12) until dis¬ 
tinctly acid (not over 2.5 per cent strong HC1), warm for a few minutes on a 
water bath, shaking frequently Filter, wash by suction, and drain the water. 1 

1 For preliminary practice use solutions of AsCb, SbCl 3 and SnCl 4 con¬ 
taining 2.5 per cent free cone. HC1, and precipitate the sulphides by saturat¬ 
ing with H 2 S. 


THE METALS 


75 


II. 


Filtrate.— 

Reject. 


Precipitate.—AS 2 S 3 , As 2 S 6 , yellow; Sb 2 S 3 , St^Ss, orange; 

SnS, brown, SnS,, yeUow. (PtS 2 , AiuSi-s, Se, Te, Mo.) Trans¬ 
fer to a small beaker, add 10 cc. HC1 (sp. gr. 1 . 2 ), and digest 
for 10 minutes, placing beaker in boiling water; stir frequently, add 5 cc. HjO, 
filter, and wash once with 5 cc. of water. 


Ill 


Precipitate.—As J3 5 (PtS 2 , Au,etc.). Wash with HCl(sp gr. 1.12) 
once, and finally with hot water. Warm the residue with about 
10 cc. HC1 (sp.gr. 1.12); add KClOs a crystal at a time,until the 
precipitate dissolves. Skim off the sulphur with a spatula. (If 
Pt and Au are to be tested, evaporate the solution to small bulk 
(2-3 cc.). A yellow precipitate indicates Pt. Filter and test 
the residue for Pt as below). The solu¬ 
tion contains H 3 As0 4 (AuCl3, etc.). 
Make solution alkaline with NH*OH; 
(Filter if ppt. forms = Hg) add several 
drops of magnesia mixture, rub sides of 
test tube with glass rod. A crystalline, 
whitish precipitate forming slowly, espe¬ 
cially where the rod has touched the sides 
of the tube, proves the presence of 
Arsenic. (If gold is to be tested for, it will pass into the 
filtrate together with the rare elements of the group, Se, Te, 
and Mo.) The method of detection is given below. Arsenic 
may be tested by the Gutzeit or Marsh test in place of 
the method above given, when the detection of gold is not 
desired. 


Precipitate.— 
K 2 PtCl e , yellow. 
Dissolve in 2 cc. hot 
water add a few 
drops of KI solu¬ 
tion; a deep red is 
due to K 2 Ptl6. 


Filtrate.— 
Sb+ + + Cl,-, 
S n ++++Cl 4 ~ 
Dilute to 
50 cc. with 
water; heat 
to about 90°; 
saturate with 
H 2 S (5 min.), 
keeping solu¬ 
tion hot; add 
5 cc. water 


Solution contains AuCL, etc. Add 5 cc. of a saturated 
solution of oxalic acid; evaporate to about 3 cc.; make acid if 
necessary with more H 2 C 2 O 4 , and add 10 cc. H 2 O. Digest on 
water bath several minutes—purple or dark yellow is due to 
Au. (Rarer elements will be in the filtrate if solution is 
filtered.) 


and again 
pass in H 2 S. 
Filter while 
hot. 




















76 


QUALITATIVE ANALYSIS 


IV. 


Precipitate. Sb 2 S 3 , 
orange red. 

Confirm. Dissolve 
in a few drops of HC1 
(sp gr. 1 12). Pour the 
solution over a platinum 
foil on which is placed a 
piece of tin. After sev¬ 
eral minutes add a little 
water and remove Pt 
foil and wash carefully. 
A black stain, insoluble 
in NaCIO, proves Anti¬ 
mony. 


Filtrate. Sn + + ++ Cl 4 - . To insure removal of 
Sb, add 5 cc. H 2 0, then pass in H 2 S to hot solution; 
filter if precipitate forms. Allow the solution to cool, 
and then pass in H 2 S for 5-10 minutes. If a yel¬ 
lowish or brownish precipitate begins to form, tin is 
indicated. 

Confirm.—Evaporate to 5-10 cc.; pour over a 
piece of zinc (C.P. about 1 g.). Tin will precipitate 
in a spongy form over the zinc. Wash by decanta¬ 
tion. Remove the Zn. Scrape off and dissolve spongy 
Sn in 2-5 cc. hot HC1 (1.20) (Pt hastens action.) 
Add 1-2 cc. water and filter, allowing filtrate to drop 
into 2-3 cc. HgCl 2 solution. A white or gray ppt. 
proves Tin. 








THE METALS 


77 


Optional Method of the Analysis of the Soluble H 2 S Subgroup 


The processes I and II of precipitating arsenic antimony and tin as sulphides 
.nd separating arsenic from antimony and tin by means of HC1 (sp. gr. 1.20) 
.re the same as in the first method, sections I and II. 


Precipitate.—As 2 S 5 
Transfer to a test tube; add 
1-4 cc. of strong HN0 3 ; 
)oil until the precipitate dis¬ 
solves: test (A) make slight- 
y alkaline with NH 4 OH, 
ind add three grams of solid 
^H 4 C1 and a piece of mag- 
lesium ribbon. Insert a 
oose cotton plug; cover the 
nouth with a piece of filter 
Daper moistened withHgCL- 
[n 10 to 15 minutes a brown 
Dr black stain will appear 
Dn the paper if Arsenic is 
present. 

Test (B) Follow direc¬ 
tions in 7—under reactions 
tor Arsenic. 


Filtrate.—Sb+ *-+Cl 3 “, Sn + + ++ Cl 4 “. Heat 

to boiling to remove hydrogen sulphide, allow to 
cool, and divide in two portions. 

1. Pour the solution in a test tube and insert 
two iron nails. Heat, adding more HC1 if 
necessary to generate hydrogen. Antimony is 
precipitated on the nails and may be tested as 
described in (a). SnCl 4 is reduced to SnCl 2 . 
Filter quickly into 1 cc. of a solution of HgCl 2 ; a 
white or gray precipitate resulting shows tin to 
be present. 

2. Pour the second portion into a small 
evaporating dish containing a platinum foil in 
contact with a piece of zinc or tin. Antimony 
will deposit as a black stain on the platinum 
and may be confirmed according to ( a ). Tin 
will precipitate in spongy form and may be 
treated according to (6). 


(a) The stain of metallic antimony 
is insoluble in NaOCl and in NaOBr. 
If the stain is dissolved in fuming nitric 
acid, and the nitric removed by warm¬ 
ing in the presence of a little tartaric 
acid until brown fumes cease, a few 
drops of HC1 added, the solution di¬ 
luted and H 2 S passed in, an orange 
colored precipitate will prove Sb 2 S 6 . 


(6) The metallic tin may be brought 
into solution by boiling with strong 
HC1 in presence with a platinum foil. 
The filtrate may now be tested with 
HgCl 2 solution. The precipitate 
indicates reduction by tin. NH 4 OH 
will blacken the precipitate. 











78 


QUALITATIVE ANALYSIS 


Notes on the Soluble H 2 S Subgroup, B 

I. If a finely divided white or fight yellow precipitate forms on the 
addition of HC1 to the filtrate of the insoluble H 2 S subgroup, the precipitate 
is largely sulphur, and the presence of the soluble group is doubtful. A pro¬ 
nounced yellow color indicates arsenic or tin; an orange color indicates 
antimony. If CuS or HgS is present, the precipitate will be dark. 

The acidity should not exceed 2.5 cc. strong HC1 per 100 cc. of solution; 
otherwise tin will not be completely precipitated. ■ 

II. Since Sb 2 S 5 dissolves but slowly, digestion with HC1 (sp.gr.l. 2) must be 
continued several minutes to insure its solution. Boiling is avoided to pre¬ 
vent the volatilization of HC1, thus weakening the solution and to avoid 
dissolving arsenic sulphide, which may occur by direct boiling. In case 
As 2 S 3 dissolves, it will appear in the Sb test. The stain of arsenic, however, 
is soluble in a hypochlorite, whereas antimony is not. 

The separation of arsenic from antimony may also be accomplished as 
follows: 

Add a few crystals of FeS0 4 to the solution containing the arsenic and 
antimony compounds. Construct a generator, as described in the Marsh 
test, with a delivery tube passing into a beaker, containing a solution of silvei 
nitrate, in place of the hard glass tube. When the hydrogen begins to be 
freely evolved, add the solution to be tested. Stibine and arsine entering 
the silver solution will immediately produce a precipitate of metallic silvei 
and silver antimonide, arsenic remaining in solution. The silver that still 
remains in the ionic form may be removed from the solution by precipitating 
it out as a chloride by the addition of HC1 (1.12), drop by drop, as long as a 
precipitate forms. By filtration a separation is effected of antimony anc 
arsenic, since the latter passes into the filtrate. Arsenic may be thrown oul 
as yellow As 2 S 3 by H 2 S. Antimony remains in the precipitate with th( 
metallic silver. Tin, if present, remains in the generator flask. 

III. KC10 3 in concentrated HC1 forms Cl 2 +CIO 2 , etc. The former acts 
as a catalyzer, causing the arsenic to dissolve, as it forms the soluble H 3 AsO 
in the presence of an oxidizing agent. Nitric acid may be used in place ol 
KC10 3 . 

Magnesium ammonium arsenate is somewhat soluble in water, hence th< 
solution should be concentrated. A strong solution of NH 4 OH decreases 
the solubility of the arsenate. Precipitation is promoted by stirring 
Care must be taken, however, not to scratch the test tube with the rod, as 
this will give rise to an erroneous inference. 

On dissolving the precipitate in HC1 and adding H 2 S, a slow formatioi 
of the sulphides of arsenic, which is characteristic of that element, takes place 


THE METALS 


79 


If AgNOs is added to a strictly neutral solution of arsenic, a brick-red 
recipitate, Ag 3 As(> 4 , forms. If the sulphides have not been washed free of 
IC1, white AgCl will precipitate. Ammonium molybdate solution warmed to 
0° with an arsenic compound precipitates ammonium arseno-molybdate, 
ellow. 

Platinum.—Platinic chloride is soluble in water; the addition of KC1 will 
.ecrease its solubility. 1 A yellow color in the arsenic solution indicates its 
>resence. With KI red K 2 Ptl 6 forms. 

Gold is precipitated in metallic form in the presence of ammonium oxalate 
Vhen the solution is hot and slightly acid. The elements Se, Te, and Mo 
emain in the solution in the form H 2 Se0 3 , H 2 Te0 3 , H 2 M 0 O 4 . 

IV. The separation of antimony from tin depends, in the first method, 

I ipon the insolubility of Sb 2 S 3 in hot 8 per cent solution of HC1, while tin 
ulphide is soluble. Cooling the filtrate and diluting precipitates tin as SnS 2 . 

In the confirmation of tin, zinc must not be allowed to dissolve completely, 
IS in that case tin would also dissolve. The electromotive series is taken 
advantage of here as it was in the case of antimony. In the latter case tin 
s used in place of zinc to avoid the precipitation of any tin that might be 
Present. Should zinc be used, as in case of the second method of separation, 
in collects upon the zinc, and antimony upon the platinum foil. 

The iron nail reduces SnCl 4 to SnCl 2 , the latter oxidizing rapidly in the air 
50 that it is necessary to filter the solution quickly into the HgCl 2 reagent. 

CLASSROOM REVIEW 

1. Study the Table of Reactions of the group in Part V, write the reactions 
Indicated. 

2. What is the approximate strength of a cold saturated solution of HC1? 
What is the strength of a boiling solution and of the solution of the acid that 
I distills over? 

3. What is the purpose of adding KC10 3 in section III, first mentioned? 

4. What are the following: tartar emetic, bronze, pewter, Paris green, 
|3cheele’s green, purple of Cassius? 

5. Name the metals belonging to the insoluble and the soluble H 2 S 
subgroups. 

I 6. What compounds are formed by the action of (NH4)2S X on the sul¬ 
phides of arsenic, antimony and tin? 

j 7 . Why is yellow ammonium sulphide used in place of the colorless 
ammonium sulphide for dissolving the sulphides of arsenic, antimony and 
tin? 


See Potassium in Soluble Group. 






80 


QUALITATIVE ANALYSIS 


8. How can you distinguish between BiOCl and SbOCl? 

9. Why is a white precipitate produced when yellow ammonium sulphide 
is acidified? 

10. Why is copper soluble in nitric acid and insoluble in hydrochloric 
acid? (See Electromotive Series.) 

Mention another element of this group which does not dissolve in HCI. 

11. How is metallic bismuth distinguished from metallic lead? 

12. Why is it necessary to boil off free chlorine before applying the SnCl 2 
test for mercury? 

13. Why is it advisable to destroy an oxidizing agent in a solution con¬ 
taining the H 2 S group before precipitating the members of the group with 
H 2 S? 

14. Why should the HCI concentration not exceed 2.5 per cent of strong 
HCI in the solution from which the H 2 S group members are to be removec 
as sulphides? 

15. How may metallic antimony and metallic tin (in powder form) 
be distinguished from one another? 

16. Give a simple test by which the correct acidity of the solution con- 
containing the H 2 S group may be judged for sulphide precipitation. (Spot 
test.) 

17. How may arsenous salts be distinguished from arsenic? If both 
salts are present how would you prove it? 

18. Give the colors of the sulphides of the group—(A and B divisions). 

19. Describe the Marsh and the Gutzeit tests for arsenic. 

20. How would you distinguish between arsenic and antimony, deposited 
on platinum foil by means of the zinc or tin and platinum couple? 








AMMONIUM SULPHIDE GROUP 

Aluminum and Iron Groups, Iron and Zinc Groups, Group 3 

DESCRIPTIVE 

Common Elements.—Precipitate as hydroxides by NH 4 OH : Aluminum, 
Chromium, Iron. Precipitate as sulphides by (NH 4 ) 2 S : Cobalt, Manganese, 
Nickel, Zinc (Iron). 

Rarer Elements.—Precipitate as hydroxides by NH 4 OH; Glucinum, 
Cerium, Neodymium, Praseodymium, Erbium, Lanthanum, Columbium, 
Scandium, Titanium, Thorium, Ytterbium, Yttrium, Zirconium. Precipitate 
is sulphides by (NH 4 ) 2 S : Gallium, Indium, Thallium, Uranium, Vanadium. 
See Part VI. 

leneral Characteristics. 

The elements of this group are precipitated either as sulphides 
Dr as hydroxdes on addition of ammonium sulphide to their 
solutions made alkaline with ammonium hydroxide in the presence 
}f ammonium chloride. Three of the elements are precipitated 
is hydroxides by NH 4 OH; namely, aluminum, chromium, and 
ron. Advantage is taken of this fact by the Hydroxide Method 
3 f separating these elements from the other members of the group. 
Ammonium sulphide precipitates the elements in the form of 
sulphides with the exception of chromium and aluminum, which 
undergo hydrolysis and precipitate as hydroxides. 

Individual Characteristics. 

ALUMINUM 1 

Al, at.wt. 27.1; sp.gr. 2.683; m.p. 668.7°; b.p. 2200° C.; oxide A1 2 0 3 

Aluminum is a silver-white metal, having a hardness resembling silver, 
the pure metal being softer than the impure. The metal is ductile and malle¬ 
able. It has a tensile strength of over 12 tons to the square inch. The 

lAlso spelled aluminium. 

81 



82 QUALITATIVE ANALYSIS’ 

element is a good conductor of heat and electricity. Its specific gravity 
is only y 3 Q- of that of copper. In the air the metal is coated over by a thir 
film of oxide, which prevents further action. In powdered form or in thir 
sheets at red heat it burns, forming the oxide AI 2 O 3 . Aluminum decompose! 
boiling water with evolution of hydrogen. It is an energetic reducing agen 
at its melting-point, having a great affinity for oxygen at this temperature 
Aluminum is trivalent; its salts are colorless. See list in Part V. 

Solution.—In dissolving substances containing aluminum keep in mind tha 
alumina, although ordinarily soluble in acids, is very difficult to dissolv 
when it is highly heated. It may be best dissolved in this case, by fusio; 
with sodium carbonate or with acid potassium sulphate, followed by an aci< 
extraction. The metal is scarcely acted upon by nitric acid, but is readil; 
soluble in the halogen acids and in hot concentrated sulphuric acids. 


DETECTION 

General Procedure.—The sample is brought into solution according t 
one of the procedures outlined. Silica is removed by taking the solutio 
to dryness, boiling the residue with hydrochloric acid and filtering. Tl 
members of the hydrogen sulphide group are removed as usual with H 2 ‘ 
the filtrate boiled to expel the excess of H 2 S, iron oxidized with nitric aci< 
and aluminum, iron and chromium precipitated as hydroxides by additic 
of ammonium hydroxide in presence of ammonium chloride. On treatir 
the precipitate with sodium peroxide, aluminum and chromium hydroxide 
dissolve, whereas ferric hydroxide remains insoluble. Aluminum hydroxic 
is precipitated by acidifying the alkaline solution with hydrochloric or nitr 
acid, and neutralizing with ammonia; chromium remains in solution. 

The white gelatinous precipitate of aluminum hydroxide may be coi 
firmed by adding a drop of cobalt nitrate solution and burning the filter. T1 
residue will be colored blue by the resulting aluminum cobalt compound. 

Sodium thiosulphate, Na 2 S 2 C> 3 , added to a neutral or slightly acid solutic 
containing aluminum precipitates aluminum hydroxide, upon boiling tl 
solution. Sodium sulphite or ammonium chloride added in large exces 
will also cause this precipitation. 

Alizarin S Test for Minute Amounts of Aluminum.—To about 5 cc. 
neutral or acid solution under examination add 1 cc. of a .1 per cent filter* 
solution of alizarin S (the sodium salt of alizarin monosulphonic acid) ai 
ammonia until the solution is alkaline, as shown by the purple color. Nc 
boil for a few moments, allow to cool and then acidify with acetic acid, 
red-colored solution or precipitate remaining is evidence of aluminum. 





THE METALS 


83 


CHROMIUM 

t , at.wt. 52.0; sp.gr. 6.92; m.p. 1520°; b.p. 2200° C.; oxides, Cr02j 

Cr 2 0 3 , Cr0 3 

Chromium is a steel gray, shining metal, whose fracture shows large 
irystals. It is one of the hardest and most refractory of the metals. The 
(arbidesof chromium are harder than quartz. The metal, containing 1.5 to 
> per cent carbon can only be cut and polished by diamond dust. Chromium 
5 non-magnetic. It oxidizes slowly on heating, but burns in oxygen at 
j/hite heat. 

Chromium has three valences; the divalent chromium is basic in character 
nd forms chromous compounds; the trivalent chromium is the form more 
ommonly known—it is also basic in character and forms chromic salts. In the 
exavalent form chromium acts as an acid, forming chromate. Chromium 
lerives its name from the Greek x/°<V a , meaning color, from the fact that 
is compounds are colored. The aqueous solutions of chromium are green 
r violet, chromates are yellow. Traces of the element color an aqueous 
solution. Chromic acid, Cr0 3 , is a familiar compound. A list of the more 
jommon compounds with their solubility, appearance and color is given 
ja Part V. 

Solution.—Powdered metallic chromium is soluble in dilute hydrochloric or 
ulphuric acid, it is only slightly soluble in dilute or concentrated nitric acid, 
t is practically insoluble in aqua regia and in concentrated sulphuric acid. 
Chrome iron ore is difficult to dissolve. It is important to have the material 
i finely powdered form to effect a rapid and complete solution of the sample. 
In agate mortar may be used to advantage in the final pulverizing of the 
lubstance. Solution is generally accomplished by fusion with KHSO 4 , or 
^a 2 C0 3 +KC10 3 , or NaHS0 4 +NaF, or Na 2 0 2 , or NaOH+KN0 3 . 

DETECTION 

Chromium is precipitated by hydrogen sulphide and ammonium hydroxide 
! ,s bluish-green, Cr(OH) 3 , along with the hydroxides of iron and aluminum 
members of previous groups having been removed). The chromic compound 
js oxidized to chromate by action of chlorine, bromine, sodium peroxide, or 
liydrogen peroxide added to the substance containing an excess of caustic 
.lkali. The chromate dissolves and is thus separated from iron, which 
emains insoluble as Fe(OH) 3 . The alkali chromates color the solution 
rellow. 

Barium acetate or chloride added to a neutral or slightly acetic acid 
elution of a chromate precipitates yellow barium chromate, BaCr0 4 . Addi- 




84 QUALITATIVE ANALYSIS 

tion of ammionium acetate to neutralize any free inorganic acid aids the 

reaction. 4 I 

Lead acetate produces a yellow precipitate with chromates, in neutral oi 
acetic acid solutions. 

Mercurous nitrate or silver nitrate gives red precipitates with chromates. 
Hydrogen peroxide added to a chromate and heated with an acid, sue! 
as sulphuric, nitric, or hydrochloric, will form a greenish-blue colored solution 
Chromates are reduced by hydrogen peroxide in acid solution, the action beinf 
reversed in alkaline solution. 

Reducing agents, hydrogen sulphide, sulphurous acid, ferrous salts 
alcohol form green chromic salts when added to chromates in acid solution 
Ether shaken with a chromate to which nitric acid and hydrogen peroxide 
are added, is colored a transient blue. Oxygen is given off as the color fades 

HCr 04 + 3 HN 03 = Cr(N0 3 )3+2H 2 0+0 2 

Diphenyl carbazide test.—To 5 cc. of the solution containing chromiuD 
as chromate, 2 drops of hydrochloric or acetic acid are added, and 1 drop o 
an acetic acid solution of diphenyl carbazide (0.2 gram CO(NH-NH-Cells) 
is dissolved in 5 cc. glacial acetic acid and diluted to 20 cc. with ethyl alcohol' 
A violet pink color is produced in presence of a chromate. Less tha: 
0.0000001 gram chromium may be detected. 

Chromic salts are bluish green; chromic acid is red; chromates, yellow 
bichromates, red; chrome alum, violet. 

The powdered mineral, containing chromium, when fused with sodiur 
carbonate and nitrate, produces a yellow-colored mass. 


COBALT 

Co, at.wt. 68.97; sp.gr. 8.7918; m.p. 1478°; b.p. unknown; Oxides, Co 3 0 

C02O3, CoO, C0O2 

Cobalt is a white, tough, ductile metal and like iron, is temporarily ma£ 
netic. It does not change in moist air. At a red heat it decomposes wate: 
The metal dissolves slowly in HC1 and in H 2 S0 4 and rapidly in HN0 3 . Most < 
the cobalt alloys dissolve in nitric acid. Some of the alloys (cobalt-chromiui 
alloys) require fusion with sodium peroxide followed by acid treatment t 
obtain their solution. 

Cobalt has two valences—divalent and trivalent, forming cobaltous an 
cobaltic compounds. Most of the cobaltous compounds appear red in soli 
tion or as salts with water of crystallization, and blue when anhydrou 



THE METALS 


85 


rhe concentrated solutions in presence of HC 1 are blue. A list of salts 
s given in Part V. 

DETECTION 

General Procedure.—After the removal of the elements precipitated by 
lydrogen sulphide from acid solution, a little nitric acid is added to the 
(solution to oxidize to the ferric state any ferrous salts which may be present, 
and ammonia is added until its odor is distinctly perceptible, to precipitate 
.ron, aluminum and chromium. This precipitate is removed by filtration 
and hydrogen sulphide passed through the ammoniacal solution to precipitate 
cobalt, nickel, manganese and zinc. After collecting this precipitate it is 
washed thoroughly with cold hydrochloric acid of approximately 1.C35 
specific gravity, to remove manganese and zinc. A small quantity of the 
residue is fused with borax in the loop of a platinum wire. A blue colcr 
in the cold bead indicates cobalt. This test is masked by the presence cf 
Large quantities of nickel. In this case the residue is dissolved in hydrochloric 
acid to which a few drops of nitric acid have been added and the solution 
evaporated to dryness. The residue is redissolved in water, acidified with 
hydrochloric acid and the cobalt precipitated with a hot solution of nitro-beta- 
naphthol in 50 per cent acetic acid. A brick-red precipitate indicates 
cobalt. 

Potassium sulphocyanate, KCNS, produces a red color with cobalt. 
Alcohol and ether are added to this solution and shaken. The ether layer is 
colored blue by cobalt. If iron is present a solution of sodium thio-sulphate, 
Na 2 S 2 0 3 , is added until the red color disappears, the solution filtered and then 
treated with the alcohol-ether mixture. 

Potassium Nitrite, KN0 2 , added to a neutral or slightly acid solution con¬ 
taining acetic acid, will precipitate cobalt as a yellow complex nitrite having 
the formula K 3 Co(N0 2 V 

Dicyandiamidine sulphate and sodium hydroxide solution added to a cobalt 
solution to which ammonia has been added until the color is distinctly dis¬ 
cernible, and containing from 10 to 20 cc. of 10 per cent sugar solution, will 
change the color of the solution to red or reddish violet. If large quantities 
of nickel are present the color will be yellow or reddish yellow, after which 
I the nickel will separate out in brilliant crystals, leaving the cobalt in solution, 

’ coloring it as described above. 

Ammonium sulphocyanate concentrated solution added to a cobaltous 
solution colors it blue. On dilution this becomes pink. Amyl alcohol or a 
mixture of amyl alcohol and ether 1:1, added to this and shaken, extracts this 
blue compound. Iron sulphocyanate, Fe(CNS) 3 , likewise colors the ether- 
alcohol extract red, which may mask the cobalt blue. By addition of sodium 



86 


QUALITATIVE ANALYSIS 


carbonate solution ferric hydroxide precipitates, while the cobalt color will 
remain after this treatment. 

IRON 

Fe, at.wt. 66.84; sp.gr. 7.86-7.88; m.p. pure, 1630°, wrought, 1600°, white 
pig, 1076°, gray pig, 1276°, steel, 1376°; b.p. 2460° C.; oxides FeO, 
Fe 2 0 3 , Fe 3 0 4 . 

Iron is a crystalline, silver-white metal, soft and easily welded, and mal¬ 
leable. It rusts in moist air; in finely divided form it decomposes water wit! 
the evolution of hydrogen at ordinary temperatures. With dilute acids iror 
forms ferrous salts, liberating hydrogen; with concentrated sulphuric acic 
it forms ferric sulphate, liberating S0 2 ; in hot concentrated nitric acid ii 
forms ferric nitrate with the liberation of NO. Dipped in cone, nitric acic 
and washed, the iron becomes “ passive,” and is not further acted upon by th< 
acid, and does not precipitate copper from a solution of its salts. Iron form: 
three series of compounds: the bivalent—ferrous compounds are white o: 
green, similar to the salts of the magnesium group; the trivalent—ferric salt. 
are very stable compounds and are brown or yellow; the hexavalent iroi 
forms ferric acid, known only in combination. 

Solubility.—The following facts regarding solubility should be remembered 
The element is soluble in hydrochloric acid and in dilute sulphuric acid, forminj 
ferrous salts with liberation of hydrogen. It is insoluble in concentrated I 
cold sulphuric acid, but is attacked by the hot acid, forming ferric sulphah j 
with liberation of S0 2 . Moderately dilute, hot nitric acid forms ferric nitrafi I 
and nitrous oxide; the cold acid gives ferrous nitrate and ammonium nitrat 1 
or nitrous oxide or hydrogen. Cold, concentrated nitric acid forms “ passiv 
iron/’ which remains insoluble in the acid. The oxides of iron are readil; I 
soluble in hydrochloric acid, if not too strongly ignited, but upon stron I 
ignition the higher oxides dissolve with extreme difficulty. They are readil; 
soluble, however, by fusion with acid potassium sulphate followed by a: j 
acid extraction. Silicates are best dissolved by hot hydrochloric acid cor I 
taining a few drops of hydrofluoric acid or by fusion with sodium and potas 
sium carbonates, followed by hot hydrochloric acid. The chloride, sulphat I 
and nitrate salts of iron are soluble in water. Sulphide ores and materu 
containing organic matter should be roasted and then dissolved in hydre 
chloric acid for the test solution. 


DETECTION 


Ferric Iron.— The yellow to red color in rocks, minerals, and soils is gei 
erally due to the presence of iron. 


j 




THE METALS 


87 




Hydrochloric acid solutions of iron as ferric chloride are colored yellow. 

Potassium or ammonium sulphocyanate produces a red color with solutions 
containing ferric iron. Nitric acid and chloric acid also produce a red color 
with potassium or ammonium sulphocyanate. This color, however, is 
destroyed by heat, which is not the case with the iron compound. The red 
color of ferric iron with the cyanate is destroyed by mercuric chloride and by 
phosphates, borates, certain organic acids, and their salts, e.g., acetic, oxalic, 
tartaric, citric, racemic, malic, succinic, etc. 

Potassium ferrocyanide, K.iFe(CN) 6 , produces a deep blue color with 
ferric salts. 

Salicylic acid added to the solution of a ferric salt containing no free mineral 
acid gives a violet color. Useful for detecting iron in alum and similar 
products. 

Ferrous Iron. Potassium Ferricyanide, K 3 Fe(CN) 6 , gives a blue color 
with solutions of ferrous salts. 

Distinction between Ferrous and Ferric Salts. 

KCNS gives red color with Fe+ + + and no color with Fe+ + . 

K 3 Fe(CN) 6 gives a blue color with Fe ++ and a brown or green with 

Fe + + + . 

NH 4 OH, NaOH or KOH precipitates red, Fe(OH) 3 with Fe + + + and 
white, Fe(OH) 2 with Fe++, appearing green in presence of air. 

Sodium peroxide produces a reddish-brown precipitate of Fe(OH) 3 with 
either ferrous or ferric salt solutions, the former being oxidized to the higher 
valence by the peroxide. Chromium and aluminum remain in solution, if 
present in the sample. 

MANGANESE 

Mn, at.wt. 64.93; sp.gr. 7.42; m.p. 1260°; b.p. 1900° C; oxides, MnO, 
Mn 2 0 3 , (Mn 3 0 4 ignition in air), Mn0 2 , Mn0 3 , Mn 2 0 7 . 

Manganese is a grayish white, hard, brittle metal, which oxidizes in moist 
air. It decomposes boiling water, liberating hydrogen. It is not magnetic. 
Four valences are known: divalent form in manganous compounds, trivalent 
in manganic compounds, hexavalent in manganic acid salts, and heptavalent 
in permanganic compounds. A list of compounds of manganese may be 
found in Part V. 

Solubility.—The metal dissolves in dilute acids. The oxides and 
hydroxides of manganese are soluble in hot hydrochloric acid. Manganese 
oxide is soluble in nitric acid and in sulphuric acid; the dioxide is insoluble 
in dilute or concentrated nitric acid, but dissolves in hot concentrated 
sulphuric acid and in hot hydrochloric acid. 




88 


QUALITATIVE ANALYSIS 


DETECTION 

General Procedure.—In the usual course of analysis manganese is found 
in the filtrate from the hydroxides of iron, aluminum and chromium, the pre¬ 
vious groups having been removed with hydrochloric acid, hydrogen sulphide 
and ammonium hydroxide in presence of ammonium phloride. Manganese, 
cobalt, nickel and zinc are precipitated as sulphides in an ammoniacal solution. 
The sulphides of manganese and zinc are dissolved by cold dilute hydro¬ 
chloric acid, H 2 S expelled by boiling and manganese precipitated as the 
hydroxide by addition of potassium hydroxide in sufficient amount to dissolve 
the zinc (sodium zincate). Manganese is now confirmed by dissolving this 
precipitate in nitric acid, adding red lead or lead peroxide to the strong nitric 
acid solution then heating and boiling. A violet-colored solution is pro¬ 
duced in presence of manganese. Chlorides should be absent. 

Sodium bismuthate added to a cold dilute nitric acid solution (3 :1, sp.gr. 
1.135) containing manganese, produces the violet-colored solution of perman¬ 
ganic acid. The test is extremely delicate, 0.000005 gram manganese will 
give an appreciable color in 50 cc. of solution. Chlorides should be absent. 
(Remove by adding AgN0 3 and filter.) 

Manganese in soil, minerals, vegetables, etc., is detected by incinerating 
the substance, treating the ash with nitric acid and taking to dryness, the 
residue is taken up with water and the mixture filtered. To the filtrate is 
added a few cc. of 40 per cent ammonium persulphate and a little 2 per 
cent silver nitrate solution. A pink color is produced in presence of man¬ 
ganese. 

Manganese compounds heated with borax in the oxidizing flame produce 
an amethyst red color. The color is destroyed in the reducing flame. 

Fused with sodium carbonte and nitrate on a platinum foil manganese 
compounds produce a green-colored fusion (“ Robin egg blue ”)• 

NICKEL 

Ni, at.wt. 68.68; sp.gr. 8.6-8.9; m.p. 1452°C.; oxides, NiO, Ni 2 0 3 , Ni 3 0 4 

Nickel is a silver-white, tough, ductile metal, whic^i is not oxidized in 
the air. At red heat it decomposes water. Its compounds are like those of 
cobalt. The metal is magnetic. With water of crystallization or in solution 
nickelous salts are green, in the anhydrous form they are yellow. The green 
solution becomes colorless in presence of cobalt (3 Ni : 1 Co). 

The determination is required in the analysis of ores, metallic substances, 
alloys, etc. 

Solubility. The element is soluble in dilute nitric acid, slightly soluble 



THE METALS 


89 


in hydrochloric acid and in sulphuric acid. The materials in which nickel 

( occurs ordinarily may be brought into solution by treatment with acids. 
Certain refractory ores and alloys require fusion with sodium carbonate or 
potassium bisulphate before treating with acid. See List of Salts in Part V. 

DETECTION 

General Procedure.—After bringing the sample into solution silica is 
I removed, if present, in the usual manner, by evaporating the solution to dry¬ 
ness in the presence of an excess of hydrochloric acid, dissolving the residue 
| and boiling with hydrochloric acid and filtering off the silica. Hydrogen 
! sulphide is then passed through the solution to remove the elements precipi¬ 
tated by this reagent. The filtrate from this precipitation is then boiled 
to expel the excess of hydrogen sulphide and a little nitric acid added to 
oxidize any ferrous iron to the ferric state. Ammonium hydroxide is then 
added to precipitate iron, aluminum and chromium. Cobalt, nickel, man¬ 
ganese and zinc are precipitated from the filtrate by adding a solution of 
colorless ammonium sulphide or by passing hydrogen sulphide through the 
ammoniacal solution. Manganese and zinc are separated from the precipitate 
by washing with cold hydrochloric acid of about 1.035 sp. gr. A small quantity 
of the precipitate is fused with borax in the loop of a clean platinum wire. A 
green color in the cool bead indicates nickel. Fairly small quantities of cobalt 
interfere with this test, so if the bead is colored blue it will be necessary to 
make further tests for nickel. 

Dimethylglyoxime will precipitate nickel as oxime from an acetic acid 
solution containing sodium acetate, in this manner separating it from cobalt, 

I manganese and zinc. After precipitating iron, aluminum and chromium and 
filtering them off, the solution is slightly acidified with hydrochloric acid, then 
is neutralized with sodium hydroxide, and acidified with acetic acid. A solu- 
tion of dimethylglyoxime is added, when nickel, if present, will be precipitated 
as a flocculent red precipitate. Precipitation takes place readily in an am¬ 
moniacal solution. Traces of nickel give a pink color with the reagent. 

Nickel may be detected in the presence of cobalt by adding a solution of 
sodium hydroxide to the solution of cobalt and nickel until a slight precipitate 
: is formed, then somewhat more potassium cyanide than is necessary to redis- 
solve the precipitate and finally two volumes of bromine water. Warm 
gently and allow to stand for some time. If a precipitate of nickel hydroxides 

[ separates, filter, wash and test with the borax bead. 

Nickel may also be detected in the presence of cobalt by precipitating the 
cobalt as nitrite, and then precipitating the nickel as hydroxide with sodium 
hydroxide and bromine water and testing the precipitate with the borax bead. 



90 


QUALITATIVE ANALYSIS 


Alpha benzildioxime added to an ammoniacal solution of nickel precipitates 
an intensely red salt having the composition C28H 2 2N 4 04Ni. This precipitate 
is very voluminous. Silver, magnesium, chromium, manganese and zinc do 
not interfere with this reaction. 

ZINC 

Zn, at.wt. 65.37; sp.gr. 6.48 to 7.19; m.p. 419°; b.p. 920°; ZnO oxide. 

Zinc is a bluish white crystalline metal; brittle at ordinary temperatures; 
malleable at 100°; brittle at 200°. Its hardness is between that of tin and 
copper. At boiling temperature the metal burns in the air with a pale greenish- 
blue flame, forming zinc oxide. In moist air the metal is coated with a stable 
carbonate which acts as a protection against further action. Zinc is used in 
galvanizing iron to protect it from corrosion by oxidation, in this respect 
acting more perfectly than tin. Zinc forms an important constituent in a 
number of alloys. At red heat zinc decomposes water; in powdered form, it 
acts on cold water. 

Solubility.—Pure metallic zinc is not readily attacked by acids, but a 
trace of impurity acting as a catalyzer causes it to dissolve. The metal dis¬ 
solves in alkalies, impurities assisting the reaction. Cold dilute HN0 3 
dissolves Zn with evolution of N 2 0 and NO. Strong HN0 3 has only a slight 
action, the nitrate being sparingly soluble in HN0 3 . Hot cone. H 2 S0 4 
dissolves Zn with evolution of S0 2 . 

Salts.—All zinc salts are soluble in NaOH, KOH, and NH 4 OH, except 
ZnS. Zn 2 Fe(CN) 6 is insoluble in NH 4 OH and in HC1. ZnS is soluble in 
dilute HCl. The sulphide, basic carbonate, phosphate, arsenate, oxalate, 
and ferrocyanide of zinc are sparingly soluble in water. A list of compounds 
of zinc may be found in Part V. 

DETECTION 

General Procedure.—After the removal of the HCl and H 2 S groups, 
Fe, Al, and Cr may be precipitated as hydroxides, or as basic acetates. Zn 
is now precipitated with Co, Ni, and Mn from an ammoniacal solution by 
H„S. The precipitated sulphides are treated with cold dilute HCl, where¬ 
upon Zn and Mn dissolve as chlorides. After expelling H 2 S by boiling, Zn 
is changed to the soluble Na 2 Zn0 2 by an excess of NaOH, which precipitates 
Mn as the hydroxide. From the alkaline filtrate white ZnS is precipitated 
by H 2 S. 

The finely powdered material, when heated on charcoal in the reducing 
flame of a blowpipe, gives an incrustation, yellow when hot—white when cold. 






THE METALS 


91 


>n moistening with cobalt nitrate solution and reigniting, the mass is greenish- 
ellow. Materials containing about 5 per cent Zn will give positive tests. 

In case the material is of interest, only if it carries higher than several 
er cent of zinc, a shorter and easier wet test is to bring the material into 
olution by means of hydrochloric or nitric acid, add bromine water and then 
•recipitate iron, aluminum and manganese with ammonia and bromine, 
Iter, wash and make the filtrate acid with hydrochloric acid, 10 cc. excess 
»eing added for each 100 cc. of solution. Now potassium ferrocyanide is 
,dded, whereupon zinc gives the characteristic precipitate Zn 2 Fe(CN)6. Cop- 
>er interferes and if present must be separated with hydrogen sulphide. 

In case manganese and copper are known to be absent, a still shorter test 
nay be used: To the solution of the zinciferous material add 2 or 3 grams of 
itric acid per 200 cc. solution, then make ammoniacal, add ferrocyanide— 
; white precipitate indicates zinc. 

Alkali hydroxides precipitate Zn(OH) 2 , soluble in excess. Ammonium 
sulphide and also Hydrogen Sulphide precipitate white ZnS from neutral or 
icetic acid solutions. The sulphide is insoluble in KOH. 





92 


QUALITATIVE ANALYSIS 


LABORATORY EXERCISES 

Chemical Reaction of the Ammonium Sulphide Group 

A. Action of a Phosphate.—Ascertain the effect of a soluble 
phosphate, e.g., Na 2 NH 4 P0 4 , on, first, acid solutions, then 
alkaline solutions containing the ions of iron, aluminum, chro¬ 
mium, cobalt, nickel, manganese, zinc, barium, calcium, strontium, 
magnesium, using separate solutions of each. Do the precipitates 
formed in the alkaline solutions (NH 4 OH) dissolve on the addi¬ 
tion of ammonium acetate and free acetic acid? Does an excess 
of a solution of an iron salt remove the phosphate ion? 

B. Organic Matter.—Use a sugar solution and note the 
effect on the precipitation of the members of the (NH 4 ) 2 S group. 

C. Oxalic Acid.—What elements of the list above mentioned 
are precipitated in presence of ammonium oxalate by addition of 
NH 4 OH? 

ALUMINUM A1+ + + 

Use a solution of AICI 3 or K 2 A1 2 (S0 4 ) 4 . 

1. To a portion add NH 4 OH in slight excess. 

Reaction (a): AICI 3 + 3 NH 4 OH = j Al(OH) 3 white gelatinous +3NH 4 C1. 

Note. —In practice it is customary to add NH 4 C1 to prevent precipitation 
of Mg, and Zn. See Introduction, Solubility Product. What effect has this 
salt on Al(OH) 3 ? 

The precipitate is soluble in a 2.5 per cent HC1 solution 
(sp.gr. 1.2). 

(6) A1 (OH) 3 +3HC1 = A1C1 3 +3H 2 0. 

2. To another portion add an alkali acetate solution. Di¬ 
lute largely and heat to boiling. The precipitate in the hot 
solution is basic aluminum acetate, soluble in acids. 

Reactions.—(a) A1C1 8 +3NH 4 C 2 H 3 0 2 = A1(C 2 H 3 0 2 ) 3 +3NH 4 C1. 

(6) Hot solution A1(C 2 H 3 0 2 ) 3 +H 2 0 +± j A1(0H)(C 2 H 3 0 2 ) 2 +HC 2 H 3 0 2 . 







THE METALS 


93 


3. Pass in H 2 S into a portion: 

(а) In acid solution no precipitate forms. 

(б) Add NH4OH and H 2 S or (NH 4 ) 2 S. 

Reaction.—(a) 2 A 1 C 13 + 3 (NH 4 ) 2 S = A 1 2 S 3 + 6 NH.iC 1 and 
AI 2 S 3 + 6 H 2 O = 1 2A1(0H) 3 + T 3H 2 S. 

N 0 t e — The hydroxide precipitates, not the sulphide, since the latter is 
ydrolyzed by water. 

4. Test the solubility of Al(OH) 3 in an excess of NaOH or 
COLL Note that the hydroxide dissolves. Aluminum interact¬ 
ing with the strong base to form the soluble sodium aluminate. 
tee Introduction—Amphoteric Electrolytes. 

Reaction.—Al (OH) 3 + 3 NaOH = Na 3 A10 3 +3H 2 0. 

5. Neutralize the solution obtained in No. 4 with an acid; 
U(OH) 3 again precipitates. 

Reaction.—Na 3 A 10 3 -t- 3 HCl = J, Al(OH) 3 -!-3NaCl. 

The precipitate dissolves with an excess of acid according 
x> the reaction (6) in No. 1. 

6. Confirmatory test for aluminum is made to distinguish it 
? rom silica, if present. Dissolve the precipitate Al(OH) 3 in 5 cc. 
}f HN0 3 (sp. gr. 1.2). (Use only a portion if the precipitate is 
large.) Add 4-5 drops of N/100 Co(N0 3 )2. 

Evaporate the solution to dryness, then add a drop or so of 
water, and soak up the liquid on a small piece of filter paper. 
Roll up the paper and ignite in a flame, holding the paper in the 
spiral of a platinum wire. Drop the ash in a crucible and heat 
fco destroy the carbon. A blue residue in the ash is due to an 
aluminum cobalt compound (Notes). 

7. Alizarin S test. See under the descriptive portion for Alum¬ 
inum 11 Detection,” page 82. 



94 


QUALITATIVE ANALYSIS 


CHROMIUM 

Under the description for this element it was learned that 
in the divalent and trivalent forms, chromium was basic in 
character, forming chromous and chromic salts with acids; and 
that in the hexavalent form chromium acted as an acid forming 
with bases the familiar compounds known as chromates. The 
two latter forms will be considered, chromous compounds being 
of less importance. 

Examples (a) CrO+2HCl = CrCl 2 +H 2 0 Chromous salt. 

(5) Cr 2 0 3 +6HC1 = 2CrCl 3 +3H 2 0 Chromic salt. 

(c) SCr0 3 +6K0H = 3K 2 Cr0 4 +3H 2 0 Chromate. 

For the tests use a choice of the following: 

Chromic Salts.—CrCl 3 , Cr 2 (S0 4 ) 3 1 , Cr(N 0 3 ) 3 , Cr 2 (S0 4 ) 3 ; Chromates, 
Na 2 Cr0 4 , K 2 Cr0 4 , or Cr0 3 . 

Formation of Chromates from Chromic Salts by Oxidation. 
Requisites.—An alkaline solution of a chromic salt and a suitable 
oxidizing agent. (H 2 0 2 , Na 2 0 2 , KMn0 4 , Br, Cl, I, etc.) 

. Example A 2CrCl 3 + lONaOH+30 = 2Na 2 CrO 4 + 6NaCl + 5H 2 0. 

8. To a solution of chromic salt, CrCl 3 , add sufficient NaOH 
to precipitate the hydroxide (Cr(OH) 3 ) and cause its solution 
(Na 3 Cr0 3 ). Now add hydrogen peroxide, H 2 0 2 , and heat the 
solution to boiling. A yellow color will be evident, due to the 
formation of sodium chromate. 

Reaction.— 

2CrCl 3 + 10NaOH-|-3H 2 O2 = 2Na 2 Cr0 4 (yellow)4-6NaCl+8H 2 0. 

Note. The result may be accomplished by addition of sodium peroxide 
alone in place of NaOH and H 2 0 2 , since Na 2 0 2 in presence of water decom¬ 
poses, yielding NaOH and O. 

1 The ignited chloride and sulphate salts are insoluble in water and in acids. 




THE METALS 


95 


Formation of Chromic Salt from a Chromate. Requisites.— 

.n acid solution of a dichromate (chromate+acid = dichromate *) 
nd a reducing agent. (H 2 S, S0 2 , HC1 concentrated, HI, 
0 2 , etc.) 

Example B.—2K 2 Cr0 4 +2HN0 3 = K 2 Cr 2 0 7 +2KN0 3 +H 2 0 and 
K 2 Cr 2 0 7 +H 2 SO 4 +3SO 2 = Cr 2 (SO 4 ) 3 +K 2 SO 4 +H 2 0. 

9. Acidify a solution of potassium chromate, K 2 Cr(>4, with 
IC1 added in excess. Note the change of color from yellow to 
range red due to the formation of the dichromate. Now pass 
a H 2 S gas (S0 2 may be used if preferred). Note the change of 
olor from orange to green, due to the reduction of the dichromate 
o the chromic salt. 

Reactions.—(a) 2K 2 Cr0 4 +2HCl = K 2 Cr 2 0 7 +2KCl+H 2 0. 

(6) K 2 Cr 2 0 7 +8HCl+3H 2 S = 2CrCl 3 +2KCl+ | 3S+7H 2 0. 

N 0 t e . _The formation of sulphur is shown by the cloudiness of the solu- 

ion. 

Hydrochloric acid alone will reduce the chromate if present in sufficient 
imount. 

K 2 Cr 2 0 7 + 14HC1 = 2 CrCl 3 +2KC1 + T 3C1 2 +7H 2 0. 

In the regular course of complete analysis of a mixture of 
compounds chromium appears as chromic chloride in the filtrate 
rom the H 2 S group. The compound is precipitated as a hydrox¬ 
ide then, oxidized to the chromate form and there identified. 

10. (a) Add to a solution of chromic salt, CrCl 3 , a slight 
gxcess of NH4OH and boil until only a faint odor of NH 3 remains. 
Note the color of the precipitate. 

Reaction.— CrCl 3 +3NH 4 OH = Cr(OH),(green)+3NH 4 Cl. 

Note. _Slightly soluble in excess of NH 4 OH with formation of violet solu¬ 

tion from which Cr(OH ) 3 is precipitated on boiling. 

1 A dichromatic+an alkali forms a chromate. 





96 


QUALITATIVE ANALYSIS 


(b) Test the solubility of Cr( 0 H )3 in a solution of a strong 
base—NaOH or KOH. The hydroxide dissolves, forming 
NasCrOs or K 3 Cr 03 - 

Reaction.—Cr(OH) 3 +3NaOH <=» Na 3 Cr0 3 +3H 2 0. 

Boiling the chromite solution reverses the action, causing Cr(OH) 3 to pre 
cipitate. 

(c) Does the addition of NH 4 C1 cause solution of Cr(OH) 3 * 

11 . To a solution of chromic salt, made alkaline with NH4OH 
add a few cc. of (NH 4 ) 2 S or pass in H 2 S gas. Note the color 0 : 
the precipitate. 

Reactions.—(a) CrCl 3 +3(NH 4 ) 2 S = Cr 2 S 3 +6NH 4 Cland 

(6) Cr^+GHijO = f2Cr(OH) 3 (green ppt.)-f t3H 2 S. 

Compare the reaction with Experiment 3 under aluminum. 

12 . Collect the chromic hydroxide precipitate, obtained ii 
Experiment 3 or 4, on a filter, transfer to a porcelain dish, dissolv( 
in a few cc. of cold 2N-HC1 (sp.gr. 1.035), make alkaline witl 
NaOH and add Na 2 0 2 in small portions until about 2 gram:, 
has been added. Note whether a precipitation takes place 
Heat, until effervescence ceases, to decompose the peroxide 
What change has taken place in the chromic salt? Consul 
Reaction in Experiment 8 . 

Note. NaOH precipitates Cr(OH) 3 , soluble in excess with formatioi 
of Na 3 Cr0 3 from which solution Cr(OH) 3 is precipitated on boiling (distinctiv. 
from aluminum). 

13. Acidify a portion with strong HNO3 (sp. gr. 1.42) an( 
then make alkaline with NH4OH. Does a precipitate form 
What changes take place by acidifying the chromate and agaii 
making alkaline? Consult Experiment 9. 

Confirmatory Tests for Chromium 

14. Add sufficient acetic acid to make the solution, remaininj 
from Experiment 12 , slightly acid. Now add a solution either 0 



THE METALS 


97 


ad acetate or barium acetate. Note the precipitate is 
illow. 

Reaction.—(a) Na 2 Cr 04 +Pb(C 2 H 3 02)2 = | PbCr0 4 yellow +2NaC 2 H 3 0 2 . 

(6) Na 2 Cr 04 +Ba(C 2 H 3 0 2 ) 2 = i BaCr0 4 yellow 
+2NaC 2 H 3 0 2 . 

15. Oxidation Test of a Chromate may be made as follows: 
ilter and dissolve the precipitate by pouring repeatedly over it 
TO cc. HNO 3 (1.07). To the cold filtrate in a test tube add about 
cc. of ether and 1 cc. of a 3 per cent solution of H 2 O 2 . Shake 
ell. A blue color is imparted to the ether layer, probably due 
. the formation of HOO 4 , perchromic acid. 

16. Reduction Test.—Solutions of chromates are yellow; the 
;llow color changes to orange red by additions of acids 
= M 2 Cr 2 C> 7 ) and is restored by adding alkalies ( = M 2 Cr 04 ). 
tie acid solution treated with a reducing agent (H 2 S, SO 2 , strong 
Cl, etc.) changes from an orange red to green. Keating assists 
e reduction. 

Not e .—The chromate yellow is restored by making the solution alkaline 
th NaOH or KOH and adding Na 2 0 2 . 

IRON, Fe++, Fe+ + + 

In the usual course of analysis iron is present in the filtrate 
om the H 2 S groups in the ferrous form. (Experiment 26, Note, 
ider Ferric Iron.) In the confirmatory tests in its detection 
in exists in the solution as a ferric salt. The student should 
hcome familiar with characteristic of both forms of iron, by 
I boratory experiments, testing ferrous and ferric salts in solu- 
bn with the reagents used in separating iron from other elements 
i its group and in establishing its identity. 

Ferrous Iron.—In the following tests 5 cc. portions of the 
rrous solution may be used. 



98 


QUALITATIVE ANALYSIS 


17. Preparation of the Ferrous Solutions.—Place 150 cc. of dis¬ 
tilled water in an Erlenmeyer flask, add a few crystals of FeSO^ 
or (NH 4 ) 2 Fe(S0 4 )2, then add 10 cc. of dilute H 2 S0 4 (1 :1) and 
several pieces of bright pure iron wire (rust removed by sand¬ 
paper). Close the flask with a stopper through which passes 
a glass tube connected with a rubber tube, 2 inches long, closed 
at the upper end and having a slit §-inch long cut through it 
wall between the glass tube and the closed end. (Bunsen valve. 
This valve permits the passage of gas from the flask, but prevent 
an intake of air. Gently heat the solution # until gas bubble 
begin to evolve. By this procedure any ferric iron, which ma} 
be present in the ferrous salt, is reduced. 

Reactions.—Fe 2 (S04) 3 +H 2 = 2 FeS 04 +H 2 S 0 4 . 

18. Add a few- drops of NH 4 OH to one portion in sufficien 
amount to give the solution an odor of NH 3 . Observe the color 
of the precipitate. Rapid oxidation by the air changes Fe(OH): 
white, to green and finally red Fe(OH) 3 - 

Reactions.—(a) FeS0 4 +2NH 4 0H = j Fe( 0 H) 2 +(NH 4 ) 2 S 04 . 

(6) 2Fe(0H%+0(air)+H 2 0 = 2Fe(0H) 3 . 

Test the solubility of the precipitate in HC1. 

Reaction.—Fe(OH) 3 +3HCl FeCl 3 +3H 2 0. 

19. (a) Into a slightly acid solution of ferrous salt pass H 2 
gas. Does a precipitate form? 

( 6 ) Make the solution thus treated ammoniacal, passing i 
more H 2 S. 

Reaction.— 

FeS0 4 +2NH 4 0H+H 2 S = j FeS (black ppt.) + (NH 4 ) 2 S 04 + 2 H 2 0 . 

(c) Test the solubility of FeS in dilute HC1 (2.5 per cen 
solution—sp.gr. 1.2). 

Reaction.—FeS+2HCl = FeCl 2 + TH 2 S. 




THE METALS 


99 


20. To a portion of ferrous solution add a solution of potassium 
Brrocyanide. The white K 2 Fe ++ [Fe(CN)o] which would form 
n absence of air, is rapidly oxidized by air to Fe 4 [Fe(CN)e] 3 , 

Prussian blue. 

Reaction.—4FeSO 4 +3K 4 Fe (CN) 6 +2H 2 SO 4 +O 2 (air) = 
l Fe 4 [Fe(CN) 6 ] 3 , blue ppt.+6K 2 S0 4 +2H 2 0. 

21. To another portion add potassium ferricyanide solution. 
Tie blue precipitate is known as Turnbull’s blue. 

Reaction.—3FeS0 4 +2K 3 Fe(CN) 6 = j Fe 3 [Fe(CN) 6 ] 2 , blue ppt.+3K 2 S0 4 . 

The precipitate is insoluble in HC1, but is decomposed by a 
ixed alkali as follows: 

2Fe 3 [Fe(CN) 6 ] 2 +16K0H+H 2 0+0 = | 6Fe(OH) 3 +4K 4 Fe(CN) 6 . 

22. Potassium thiocyanate or ammonium thiocyanate has 
10 action on ferrous solutions. (Ferric iron produces a red color 
'vith KCNS.) Prove this by testing a portion of the ferrous 
solution with the reagent. 

33. Oxidation of Ferrous Iron.—Boil the remainder of the 
errous solution and add strong nitric acid drop by drop until 
here is no further darkening of the solution with addition of 
nore HNO3. If a drop of this solution is placed on a white tile 
ir on paraffined white paper and a drop of fresh KsFe(CN)6 
solution (a crystal of the salt in 10 cc. H2O) no blue color will 
*esult, if the oxidation is complete. 

Reaction.—6FeS0 4 +2HN0 3 +3H 2 S0 4 = 3Fe 2 (S0 4 ) 3 + f 2N0+4H 2 0. 

Oxidation of ferrous chloride with nitric acid causes a color 
hange from colorless through brown and finally an amber yellow. 

3FeCl 2 +HN0 3 +3HCl = 3FeCl 3 + T N0+2H 2 0. 

Iron may be oxidized by KCIO 3 , H 2 O 2 , K 2 Cr 207 , KMn 04 . 
The last two reagents are used in the quantitative determination 
)f iron. 




100 


QUALITATIVE ANALYSIS 


Ferric Iron.—The tests made with ferrous iron using the solu¬ 
tion made in Experiment 17 or a fresh solution of ferric chloride, 
FeCl 3 , should be repeated following the order given below. 

In the process of analysis, iron is generally present as a chloride. 
The reactions will be written with the supposition that this salt 
is used. # 

24. (a) Add NH 4 OH to a solution of ferric salt. 

Reaction.—FeCl 3 -j-3NH 4 OH = Fe(OH) 3 , reddish brown ppt. +3NH 4 C1. 

(b) Test solubility of Fe(OH ) 3 in HC1 and in dilute HN0 3 . 
Write out the reaction. 

(c) Test the solubilty of Fe(OH ) 3 in NaOH or KOH solution 

( d ) Does the addition of NH 4 CI cause the hydroxide to 
dissolve? 

25. Add sodium or ammonium acetate to a solution of ferric 
salt, slightly acid. 

FeCl 3 +3NH 4 C 2 H 3 0 2 = | Fe(C 2 H 3 0 2 ) 3 +3NH 4 Cl. 

26. Pass in H 2 S. 

(а) Into an acid solution of ferric salt containing 2.5 cc. 

cone. HC1 per 100 cc. $ j 

Is the reaction evident? Does a precipitate form? 

(See Experiment 27 following). v 

( б ) Add NH4OH and H 2 S or (NLLi^S to a fresh sample. 

Reaction.— 2FeCl 3 +6NH 4 OH+3H 2 S = Fe 2 S 3 (brown black)+6NH 4 C1 

+ 6H 2 0. 

Note. If NH 4 OH is added to test (a) above, the reaction is the same as 
in (6) Experiment under ferrous salts, since FeCl 3 is reduced by H 2 S tc 
FeCl 2 , as follows: 2FeCl3 + H 2 S = 2FeCl 2 + 2HCl+S. 

Tests with Reagents Used for Confirming Iron 

27. Add potassium ferrocyanide to a portion of ferric solu¬ 
tion. The precipitate is Prussian blue. For best results the] 
solution should be neutral or at most only slightly acid. Delicacy 







THE METALS 


101 


>f test is 0.0000002 gram Fe in 100 cc. of solution. The color is 
aint green in very dilute solution, blue if the solution is more 
;oncentrated. With increased concentration a precipitate forms, 
lee list of ferric salts. 

Reaction. —4FeCl3+3K 4 Fe(CN) 6 = J. Fe 4 [Fe(CN) 6 j 3 , blue ppt.+12KCl. 

Note. —Potassium ferricyanide gives a brown coloration, but no pre- 
;ipitate with ferric iron solution. (A blue precipitate for ms with ferrous.) 

28. Potassium thiocyanate, KCNS, gives a deep red precipitate 
)r red or pink-colored solution according to the concentration of 
ron. (Distinction from ferrous salts.) The reaction is reversible. 
4.n excess of the reagent increases the delicacy of the test— 
1.00000007 gram Fe in 100 cc. of solution. 

Note. —KCNS also produces a color with HN0 3 . This acid, therefore, 
should be absent in the test sample. 

29. Reduction of Ferric Salts. —This is commonly accom¬ 
plished in the laboratory by H (Zn-f HC1), H 2 S, SnCl 2 , SO 2 . 

(a) Reduce FeCl 3 solution strongly acid with HC1, by adding 
SnCl 2 . The reduction takes place quickly in hot solution. 

1 (6) Reduce FeCl 3 solution by passing in H 2 S into the acid 
solution. 

What color change takes place due to reduction? Write out 
reactions for (a) and (6). 

Note. —SnCl 2 is used for the quantitative determination of iron. 

COBALT, Co++, Co+ + + 

In the general scheme of separations cobalt is found in the 
titrate of the H 2 S group as cobalt chloride. For the following 
tests a solution of Co(N 03)2 or C 0 CI 2 may be used. 

30. To a solution of cobalt salt add NH 4 OH and then an 
3 xcess of NH 4 CI. 

Note. —The blue basic salt dissolves in an excess of NH 4 OH or NH 4 C1. 



102 


QUALITATIVE ANALYSIS 


forming a brown-colored solution, which changes in the air or on boiling 
to a red or pink-colored solution. 

Reactions.—(a) CoC 1 2 +NH 4 OH = 1 Co(OH)Cl(blue)+NH 4 Cl. 

(6) Co(OH)C1+NH 4 OH = 1Co(OH) 2 (pink)+NH 4 Cl. 

(c) Co (OH) 2 +2NH 4 C1+2NH 3 = Co (NH 3 ) 4 C1 2 +2H 2 0. 

Note. —Presence of organic matter prevents precipitation of cobalt hydrox¬ 
ide as well as the presence of NH 4 salts. 

31. To the solution obtained in Experiment 30 above add H 2 S 
or (NH^S. A black-colored precipitate is obtained, insoluble 
in excess (NFU^S. (NiS tends to dissolve. See Experiment 446, 
under Nickel.) 

Reaction.— 

Co(NH 3 ) 4 C1 2 +(NH 4 ) 2 S+4H 2 0= ICoS (black)+2NH 4 C1+4NH 4 0H. 

Write out reaction with H 2 S. 

32. Dilute HC1 (sp.gr. 1.035) does not dissolve CoS. Aqua 
regia, however, dissolves the sulphide. Try this. 

Reaction.—3 CoS+8HN0 3 = 3Co(N 0 3 ) 2 + j 3S+ T 2N0+4H 2 0. 

33. Neutralize the solution with NaOH after expelling most 
of the acid by heating. A precipitate forms insoluble in excess. 

Reactions.—(a) CoCl 2 +NaOH = 1 Co(OH)Cl (blue)+NaCl. 

(6) Co(OH)Cl+NaOH = | Co(OH) 2 (pink)+NaCl. 

Note. —Co (OH) 2 is soluble in NH 4 salts. Exposure to air gives the 
black Co(OH) 3 distinction from Ni(OH) 2 , which does not oxidize with air. 

34. To the alkaline mixture of cobalt salt add KCN solution 
in excess and Br water, warm, Co(CN) 2 light-brown precipitate 
dissolves in the excess of KCN. 

Reaction.—Co(CN) 2 +4KCN = K 4 Co(CNb, brown. 




THE METALS 


103 


35. On warming in presence of an oxidizing agent a bright 
fellow colored solution is obtained. 

Reaction. —2K 4 Co (CN)«+H 2 0+O = 2K 3 Co (CN) 6 -f 2KOH. 

Note. —Nickel under the above conditions forms the black precipitate 
STi(OH) 3 , hence a separation from nickel may be affected by this procedure., 

Confirmatory Tests for Cobalt 

36. Potassium Nitrite Test.—The reagent added in excess 
bo the concentrated cobalt solution, warmed, produces a yellow 
srystalline precipitate K3Co(N0 2 )6- Addition of a saturated 
solution of potassium salt (KC1) decreases the solubility of 
K 3 Co(N0 2 )6. 

Note. —Nickel produces no precipitate with KN0 2 . 

37. Borax Bead Test.—A cobalt salt fused with borax gives a 
blue-colored bead. Try this. 

38. a-Nitroso-/3-Naphthol Test.—CioHe(NO)OH dissolved in 
50 per cent acetic acid gives a red precipitate, [CioH 6 (NO)0]3 Co 
when added to a cobalt salt. The presence of free HC1 does not 
interfere. (Nickel in presence of HC1 gives no precipitate.) ‘See 
page 112. 

MANGANESE, Mn+ + 

In the usual procedure of separation of the groups manganese 
is found in the filtrate of the H 2 S group in the divalent form. 
The salts of the oxide MnO and the acids are pink in solution or 
in crystallized form and colorless as anhydrides. 

Use a solution of MnSC>4 or MnCl 2 or Mn(N03) 2 . 

39. To a portion of the solution add NH4OH and note colors 
of the precipitate formed. Test the solubility in NH 4 C1 solution. 

Reactions.— MnCl 2 +2NH 4 OH = j Mn(OH) 2 (white)+2NH 4 C1. 

Mn(0H) 2 +0 (air) = rMn0 2 -H 2 0 (brown). 

Note. —NH4CI prevents precipitation only for a short time, as oxidation 



104 


QUALITATIVE ANALYSIS 


by air takes place and manganous acid, Mn0 2 -H 2 0, is precipitated. Separa¬ 
tion of Mn from Fe, A1 and Cr, by precipitation of these as hydroxides, is 
not complete in presence of considerable amount of manganese salt. 

The presence of organic matter interferes with the precipita¬ 
tion of manganese. 

40. To the solution obtained in Experiment 39, add (NH^S or 
pass in H 2 S gas. A pink-colored sulphide is obtained which 
darkens on exposure to the air (presence of Mn 20 s). 

MnCl 2 +2NH 4 OH+H 2 S = MnS+2NH 4 Cl+2H 2 0. 

Note. —Presence of NH 4 C1 assists precipitation of MnS, tartrates and 
oxalates retard it. In boiling with large excess (NH 4 ) 2 S, the green hydrated 
sulphide is formed. 

41. Test the solubility of the precipitate in dilute HC1 (sp. gr, 
1.035). 

Note. —The sulphide is also soluble in acetie acid. Manganese may thus 
be separated from NiS, CoS, ZnS. 

42. (a) To the solution obtained in Experiment 41, add NaOH 
and then Na 202 in excess. A dark-brown compound Mn 02 *H 20 
is formed. 

( 6 ) Test the solubility of Mn 02 -H 20 in hot dilute HNO 3 
(sp.gr. 1.2). The dark-brown residue is MnC> 2 . This affords a 
method of separating Mn from Fe, since Fe(OH )3 dissolves in 
HN0 3 . 

Confirmatory Tests for Manganese 

43. Lead Oxide Test.—(a) Place the precipitate obtained in 
Experiment 42 ( 6 ) in a small beaker, add 10 cc. of strong HNO 3 
(sp. gr. 1.42) heat to boiling and add 1-2 grams of red lead (Mn free) 
or Pb 02 . Allow to settle. The supernatant liquid will be 
colored violet red by the permanganic acid formed. 

Reaction.—2Mn0 2 +3Pb0 2 +4HN0 3 = 2HMn0 4 (violet red) +PbO 
+2Pb(N0 3 ) 2 +H 2 0. 



THE METALS 


105 


Note .—The presence of chloride interferes with the test. The precipitate, 
.herefore, should be washed free of chloride. A trace of Mn may be detected 
>y this procedure. Sodium bismuthate may be used in place of the lead 
>xide. 

( 6 ) Fuse a portion of the manganese precipitate on a platinum 
oil with a mixture of Na2CC>3 and KNO3 or KCIO3. Green 
sodium manganate will be formed. 


NICKEL, Ni++, Ni + + + 

In the general scheme of separation nickel is found in this 
^roup as NiCb. Use a solution of Ni(NOs )2 or NiCb. 

44. (a) To a solution of nickel salt add NH 4 OH. 

Reaction— NiCl 2 +2NH 4 OH = 1 Ni(OH), (green gelatinous)+2NH 4 C1. 

(b) Does a precipitate form when NH4CI is added? 

Reaction—Ni(OH) 2 +2NH 4 Cl+2NH 3 = Ni(NH ) 4 C1 2 (blue-colored solu¬ 
tion) -f2H 2 0. 

Note —Organic matter prevents pecipitation of Ni(OH) 2 as well as the 
presence of NH 4 salts. 

45. To the solution of nickel salt containing NH 4 0H and 
NH 4 CI (Experiment 44 ( 6 )) add H 2 S gas or a solution of (NH 4 ) 2 S. 

Reaction.—Ni(NH 3 ) 4 Cl 2 +H 2 S+2H 2 0 = l NiS (black) -f-2NH 4 Cl 
+2NH 4 OH. 

Write out the reaction with Ni(NH 3 ) 4 Cl 2 +(NH 4 ) 2 S. 

Notes .—If the solution contains a large excess of (NH 4 ) 2 S in presence of 
free NH 4 OH, the filtrate from NiS will be colored brown by dissolved Ni. 
From this solution NiS may be completely precipitated by boiling in presence 
of sufficient acetic acid to neutralize free NH 4 OH. No precipitate forms in 
presence of much free acetic acid, but the addition of NaC 2 H 3 0 2 causes 
precipitation. The presence of large quantities of NH 4 salts prevents the 
dissolving of NiS. 

NiS oxidizes in the air, forming water-soluble NiS0 4 . This is avoided by 
quick filtration and presence of H 2 S in the wash water. 




106 QUALITATIVE ANALYSIS 

46. Test the solubility of NiS in dilute HC1 (sp.gr. 1.035). 

Note .—The sulphide is insoluble in dilute HC1 but dissolves in aqua regia. 

Reaction.—3NiS+2HN0 3 +6HCl=3NiCl 2 + 1 3 S+ 12 N 0 + 4 H 2 0 . 

The sulphur is oxidized by HN0 3 , forming H 2 SO 4 with libera¬ 
tion of NO gas. Write out reaction. 

47. (a) Dissolve the sulphide NiS in aqua regia. Neutralize 
with NaOH and add an excess. Now oxidize the nickelous salt 
with bromine water. 

Reaction.—Ni(OH) 2 +NaOH+Br = [ Ni(OH) 3 +NaBr. 

Note— NaOH or KOH precipitate Ni(OH ) 2 insoluble in excess. The 
precipitate does not oxidize in the air as does Co(OH) 2 . 

(b) In place of the excess of NaOH add KCN to the slightly 
alkaline solution. The green precipitate is Ni(CN) 2 ; with an 
excess of KCN the precipitate dissolves forming K 2 Ni(CN) 4 . 
Heat this solution with Br water as in Experiment (a) above. 
The black precipitate is Ni(OH) 3 . 

Note. Cobalt does not precipitate under similar treatment, hence it 
may be separated from nickel by this procedure. 

Confirmatory Tests for Nickel 

48. Borax Bead Test. The borax bead is colored brown by the 
NiS. Test a mixture of CoS and NiS with a borax bead. Note 
that the blue color predominates. What inference do you draw 
from this last test? 

49. Dimethyl-glyoxime Test.—Add a 1 per cent alcoholic solu¬ 
tion to an ammoniacal solution of nickel salt. A red-colored pre¬ 
cipitate is obtained. In an extremely dilute solution a pink color 
is seen. Delicacy in 100 cc. of solution 0.00000025 g. Ni may be 
detected. 

Reaction.-2(CH 3 ) 2 C 2 N 2 0 2 H 2 +NiCl 2 +2NH 4 OH 

= 2 NH 4 CI -f [ (CH 3 ) 2 C 2 N 2 0 2 H] a N i+2H 2 0. 






THE METALS 


107 


ZINC, Zn + + 

Zinc is in the form of chloride, in the general procedure of 
analysis, in the filtrate from the H 2 S group. 

I Use a solution of ZnSC>4 or ZnCU. 

50. Ascertain the following facts: Does a precipitate form 
upon the addition of NH 4 OH? If so, note its color and ascertain 
whether it dissolves upon the addition of an excess of the reagent. 
Does the precipitate dissolve upon the addition of NH 4 CI? Does 
heating the solution cause a coagulation of the precipitate? 

Reactions.—ZnCl 2 + 2 NH 40 H = j Zn(OH)2+2NH4Cl. 

Zn (OH) 2 +2NH 4 C1+2NH 3 = Zn(NH 3 )4Cl 2 +2H 2 0. 

51. To the solution made alkaline with NH 4 OH+NH 4 CI 
add a few cc. of (NH 4 ) 2 S or pass in H 2 S gas. Note the color of 
the precipitate. Filter. 

Reaction.— Zn(NH3)4Cl2+(NH 4 ) 2 S+4H 2 0=ZnS (white) +2NH 4 C1 

+ 4 NH 4 OH. 

52. Remove a portion of the precipitate with a spatula and 
place in a porcelain dish. Pour over it about 20 cc. of cold 
2N-HC1 (1.035), stir, and note whether the precipitate dissolves. 

Reaction.—ZnS+ 2 HCl ZnCb+ T H 2 S. 

Note— ZnS, although readily soluble in mineral acids, does not dissolve 
: easily in acetic acid, and may be precipitated in presence of free acetic acid 
from its solutions by H 2 S. 

53. If solution is effected, evaporate to half its bulk, cool, 
and make alkaline with NaOH solution. Now add Na 2 0 2 in 
small portions until about 2 grams has been added. Does pre¬ 
cipitation take place? Heat to decompose the peroxide until 
effervescence ceases. If precipitation has taken place, note 
color of substance; if not, note whether the solution is colored. 

Reactions.— (a) ZnCl 2 +2NaOH = j Zn(OH) 2 +2NaCland 

( 6 ) Zn(OH) 2 +2NaOH <=±Na?Zn0 2 (sol.) +2H ? 0. 






108 


QUALITATIVE ANALYSIS 


Note .—Boiling the solution of sodium zincate causes the precipitation of 
Zn(OH) 2 . Reaction (6) therefore, is reversible. A large excess of NaOH 
prevents this precipitation. 

54. Acidify the solution with HNO 3 (1.42) and then make 
alkaline with NH 4 OH. Does a precipitate form? 

55. Acdify with 30 per cent acetic acid solution, avoiding an 
excess, add a little NaC 2 Hs 02 and heat nearly to boding, pass in 
H 2 S gas to saturation. A white precipitate is Zn . 

56. ConfirmationofZinc.—While the solution is still hot filter off 
the ZnS precipitate on a filter and dissolve by pouring repeatedly 
over it 5-10 cc. HNO3 (1.07). To the filtrate add 4-5 drops of 
N/100 Co(N 03 ) 2 ,* evaporate almost to dryness to expel the acid; 
then neutralize with Na 2 C 03 (10 per cent), adding § cc. in excess. 
Evaporate to dryness and ignite gently until the purple color 
of the cobalt disappears. Allow to cool. A green color is due 
to a compound of zinc and cobalt oxides, probably cobalt zincate, 
CoZn02. 

Notes .—The cobalt nitrate test may be made on any dry zinc compound 
by moistening with cobalt nitrate and igniting the mixture. 

ZnS may be precipitated by H 2 S from a solution of Na 2 Zn0 2 , in presence 
of NaOH. 

Table of Reactions 

The student is advised to make a study of the comparative reactions 
of the ammonium sulphide group by referring to the Tables in Part V. The 
tests may be conducted in the laboratory if desired. 




THE METALS 


109 


Outline of Separations of the Ammonium Sulphide Group 
(Iron and Zinc Groups) 

Three general procedures are considered in the order of their 
nerit for separation and detection of the members of this group. 

(а) From the chemical reactions it is evident that ammonium 
sulphide will precipitate all the metals of this group after making 
the solution alkaline with ammonia. The group is thus separated 
rom the alkaline earths and the alkalies, and the members then 
isolated by the procedure described later. This method is con¬ 
sidered the most reliable of the three, as it does not possess objec¬ 
tions of the optional methods ( b ) and (c). 

(б) If ammonia is added to a solution containing all the 
metals of the group in presence of sufficient ammonium chloride, 
the trivalent metals iron (ferric), chromium and aluminum are 
precipitated as hydroxides, while the remaining elements are in 
solution. The group is thereby divided into two sub-groups, thus 
simplifying subsequent separations. The objection to this pro¬ 
cedure is the fact that manganese and zinc, if present in small 
amounts, may be occluded and carried out of solution by the 
hydroxides of the trivalent elements and thus escape detection. 
By dissolving and reprecipitating these hydroxides this difficulty 
is largely overcome. 

(c) The third procedure is given on account of its application 
in gravimetric methods to determining manganese and zinc. 
A knowledge of this procedure is considered advisable in this 
preliminary course. This basic acetate precipitation of the 
trivalent elements occurs when sodium acetate is added in suffi¬ 
cient excess to nearly neutral solutions of ferric iron, aluminum 
and chromium and the solution diluted to a comparatively large 
volume and boiled. As in case of the ammonium hydroxide 
method the group is divided into two and each subgroup then 
treated by suitable procedures. The objection to this procedure 
is the fact that chromium is incompletely precipitated if it is 
present in relatively large amounts with small amounts of iron 


110 


QUALITATIVE ANALYSIS 


and aluminum. Under this condition the precipitation of al 
three elements is incomplete. With iron and aluminum in pre-i 
dominance the method is satisfactory. 

In the first procedure, which we may designate as the sulphide 
method, the precipitate consists of the hydroxides of aluminum 
and chromium and the sulphides of iron, cobalt, nickel, man¬ 
ganese and zinc. Cobalt and nickel sulphides are insoluble ir 
cold dilute HC1 (sp.gr. 1.035). 

The hydroxides of aluminum and chromium and the sulphides 
of the remaining elements dissolve, and pass into the filtrate when, 
the mixture is treated with cold dilute HC1 and transferred to a 
filter. The residue NiS and CoS is brought into solution with 
aqua regia and nickel and cobalt determined by means of the 
borax bead and the wet methods given in the tabulated procedure. 
The main filtrate contains the chlorides of Al, Cr, Fe, Mn and Zn, 
and an excess of HC1 with H 2 S. The greater part of HC1 and, 
all the H 2 S are expelled by evaporation and the solution then 
made strongly alkaline by addition of Na 2 0 2 . The oxidation 
converts chromic chloride into soluble sodium chromate, the 
alkali forms the water-soluble aluminate and zincate, while iron 
and manganese are precipitated as hydroxides. 

By filtration, a separation of Fe(OH ) 3 and Mn0 2 H 2 0 from, 
the solution containing Al, Cr and Zn is effected. Manganese 
and iron may be readily identified in the residue in presence of 
each other; or by separation, when a rough estimation of the 
quantity is desired. Chromium may be recognized by the yellow 
color its solution as a chromate imparts to the filtrate from iron 
and manganese. Aluminum may be precipitated from the 
solution by neutralizing the alkali with HNO 3 and precipitating 
with NH 4 OH in presence of NH 4 CI, which prevents precipitatior 
of Zn(OH) 2 , while chromium as chromate does not precipitate 
By making the filtrate from Al(OH )3 acid with acetic acid anc 
adding BaCl 2 solution chromium is precipitated as yellow BaCrCU 
Zinc may now be determined in the filtrate by precipitating a 1 
White ZnS by H 2 S. 





THE METALS 


111 


Separation of Ammonium Sulphide Group—Sulphide Method 


(а) li the solution is the filtrate of the H 2 S Group, boil it to expel sul- 
hureted hydrogen, e.g., until no odor of the gas remains, then add 1-2 cc. 
f cone. HNO3 (1-42), and boil to oxidize the iron. 

( б ) If oxalates or tartrates are present, destroy by ignition. (See Notes.) v 

(c) If phosphates are present, they should be removed. About one-tenth 
f the solution should be used to detect these interfering substances, unless 
nown to be absent, before proceeding with the analysis. (See Notes.) 

( d ) To the hot solution, free from phosphoric acid, etc., add NH 4 C1, 1 :4 
unless already present or the solution contains considerable HC1), then add 
IH4OH until the odor of ammonia is distinct upon shaking solution. If 
recipitates form, Al, Fe, and Cr may be present. Observe the color of the 
; ydroxides. Reddish brown is Fe(OH) 3 ,‘ white may be Al(OH) 3 ; and grayish 
reen or lavender, Cr(OH) 3 . Now add (NH 4 LS slowly, or pass in H 2 S, if Ni 
3 suspected, until the solution is saturated. Vapor arising from the flask will 
ihen blacken a filter paper moistened with lead acetate. Coagulate the 
;recipitate by heating and shaking. Filter immediately and wash the precipi- 
ate with 1 per cent solution of (NH 4 ) 2 S and then with distilled water, keep- 
ig the funnel covered between intervals with a watch glass to prevent oxida- 
ion by the air. 


I. 


Precipitate.—White Al(OH) 3 ; green 
)r(OH) 3 ; white ZnS; pink MnS; black 
i’eS; black NiS; black CoS. 

Tear off the portion of the filter con- 
aining the precipitate and drop into a 
mall Erlenmeyer flask. Pour over the 
ulphides, etc., 25 to 50 cc. of cold 

;N • HC1 (1.035) (1 vol. HC1 (1.20) to 6 vols. H 2 0). Cork the flask and shake 
o facilitate solution of soluble sulphides. After 4-5 minutes filter and wash 
he residue immediately with wash water containing H 2 S and NH 4 C1. 


Filtrate.—The metals of the 
(NH 4 )2C0 3 and the Soluble Group 
if present will be found here, phos¬ 
phoric acid being absent. Reject 
if these groups are not to be ex¬ 
amined. (See page 134.) 












112 


QUALITATIVE ANALYSIS 


III. 


Residue.—Black NiS, black CoS. 
(If light colored, dissolve in warm HC1 
and add to filtrate.) Test the residue 
with the borax bead. Blue indicates 
Co. Ni may be present. Yellow or 
brown indicates Ni. Co may be 
present in very smah amount. In 
case the bead is blue, tear off the por¬ 
tion of the filter containing ppts. 
Place in a casserole and add 5-15 cc. 
HC1 ( 1 . 12 ) and several drops of HN0 3 
(1.42). Warm until the black ppt. 
dissolves and filter. Evaporate almost 


Filtrate—Fe+ + +; Mn+ +; Cr+ + + * 
Al + + + ; Zn + +; Cl - ions. Evaporat( j 
to half its bulk to remove a portion oj 
the acid and to expel H 2 S. Cool, anq 
make alkaline with C.P. NaOH solu¬ 
tion. Add 1-3 grams of Na 2 0 2 in smal 
portions. The solution should nov 
be strongly alkahne. Heat until effer¬ 
vescence ceases. Filter. Wash the] 
precipitate with warm water. Analyze a 
precipitate according to method IV 
and filtrate by method VI. 


to dryness, then add 5 cc. water and NaOH, drop by drop, until the solution 
is neutral or a trace of precipitate forms. 


III. Divide into two portions, A and B. 


A. Use either of the f oho wing tests. 

1. Add 15 cc. 30 per cent sol. 
HC 2 H 3 0 2 and then 50 cc. 30 per cent 
sol. KN0 2 . Dilute to 100 cc. and 
allow to stand some time. A fine yel¬ 
low precipitate is K 3 Co(N0 2 ) 6 . 

Confirm.—Filter, wash with KN0 2 
sol. Test residue with borax bead. 
Blue indicates cobalt. If ppt. is small, 
burn filter and test the ash. 

2. Make the solution faintly acid 
with a few drops of dilute H 2 SO 4 and 
evaporate to dryness to expel HN0 3 , 
neutralize with NH 4 OH and add an 
equal volume of glacial acetic acid 
followed by an excess of a 50 per cent 
acetic solution of <x-nitroso-/3-naphthol. 
A brick-red precipitate proves the 
presence of cobalt. The precipitate, 
tested with borax in the flame, gives 
a blue-colored bead. 


B. Use either of the following 
methods. 

1 . Make the solution slightly acid 
with HC1, then neutralize with am¬ 
monia and add a sufficient excess to 
give a decided ammoniacal odor to the 
sample. Now add an excess of 1 per 
cent alcoholic solution of dimethyl 
glyoxime. A scarlet or pink-colored 
precipitate, Ni[(CH 3 ) 2 C 2 N 2 0 2 H] 2 , 
proves the presence of nickel. 

2. Add 10 per cent sol. KCN drop 
by drop until any precipitate, that 
forms, redissolves, then 2 cc. in excess. 
Heat to 50°-60° for 5 min., stirring 
frequently. Filter into a test tube. 
Add fresh cone. NaBrO until filter 
paper moistened in sol. of KI and 
starch i* colored blue or brown. For¬ 
mation of a dark ppt. indicates Ni. 
Borax bead test=brown bead. 














THE METALS 


V. Precipitate from Na 2 C >2 treatment under Filtrate III. 


113 


Precipitate.—Brownishred F e (OH) 3 ; 
ark brown MnCh • H 2 0. 

(a) For detection of Mn and Fe 
se either (a) or (6) methods. 

(а) Washppt. 

Test for Mn.—Take up small 
mount of ppt. on a Na 2 CC>3 bead, 
[CIO 3 , a bluish green or green mass 

Test for Fe.—Dissolve ppt. in HC1. 
rm with K 4 Fe(CN) 6 test = blue ppt. 

( б ) Remove precipitate from filter 
rarm with 20-30 cc. dilute HNO 3 
rash with a little warm water. 


Filtrate.—Light yellow Na 2 Cr 04 j 
colorless NasA10 3 ; Na 2 Zn0 2 . Pro¬ 
ceed to the analysis of the Aluminum 
Subgroup under VI. 


heat and dip hot bead into powdered 
is due to NaMn 04 . 

A yellow color indicates FeCl 3 . Con- 

paper and place in a casserole and 
(1.20), heat to boiling, stir, filter, and 


r. 

Residue.—Dark brown or black 
vln0 2 . 

Confirm by adding to the pre¬ 
cipitate in a test tube 1-2 grams of 
•ed lead (Mn free) and 10 cc. of 
3N0 3 (1.42). Boil 2-3 minutes, and 
illow to settle. The supernatant 
iquid will be colored violet-red by the 
permanganic acid formed. 


Filtrate.—Fe(N0 3 ) 3. 

Make strongly alkaline with 
NH 4 OH and heat to boiling to coagu¬ 
late the precipitate. A brownish red 
precipitate indicates Fe(OH) 3 . 

Confirm by dissolving precipitate 
by adding warm dilute HC1 to washed 
residue. Add a few drops of the fil¬ 
trate to 5 cc: KCNS. A deep-red 
color is due to the feebly ionized salt 
Fe(CNS) 3 , proving the presence of 
iron. 


VT. Filtrate from Na2C>2 treatment u nder Filtrate III. _ 

Acidify the filtrate, containing Al, Cr, and Zn, with HN0 3 (1.42) add 2-3 
grams of NH 4 C1 and then make slightly alkaline by the addition of NH 4 OH 
(0.96) and about 2 cc. in excess. (End points can be determined by placing 
a drop of the stirred solution on litmus paper.) Coagulate by heating almost 
to boiling. Filter and wash the precipitate with hot water. 













114 


QUALITATIVE ANALYSIS 


VII. 


Precipitate.—May be white, gelatinous 
Al(OH) 3 . If silica is suspected dissolve the pre¬ 
cipitate in 5 cc. of HNO3 (1.20). (Use only a 
portion if the precipitate is large.) Add 4-5 
drops of N/100 cobalt nitrate, Co(N0 3 )2. 

Evaporate the solution to dryness, then add 
a drop or so of water, and soak up the liquid 
on a small piece of filter paper. Roll up the 
paper and ignite in a flame, holding the paper 
in the spiral of a platinum wire. Drop the ash 
in a crucible and heat to destroy the carbon. A 
blue residue in the ash is due to an al umin um 
cobalt compound. 


Filtrate.—Cr, Zn, etc. 

Acidify with 30 per cent 
solution of acetic acid, avoid¬ 
ing over 2 cc. in excess. If 
the solution is colorless, 
chromium is absent. In this 
case proceed immediately tc 
the analysis of zinc. Ir 
case the solution is colorec 


slightly yellow, add about 10 cc. of 10 per cent solution of BaCl 2 , and allow 
to stand 5-10 min. and filter. 


VIII 


Precipitate.—Yellow 
BaCr0 4 . 

Confirmation of chromium 
may be made as follows: 
Filter and dissolve the pre¬ 
cipitate by pouring repeat¬ 
edly over it 5-10 cc. HN0 3 
(1.07). To the cold filtrate 
in a test tube add about 2 
cc. of ether and 1 cc. of a 3 
per cent solution of H 2 0 2 . 
Shake well and settle. A 
blue color is imparted to the 
ether layer, probably due to 
the formation of HCr0 4 , 
perchromic acid. 


Filtrate.—May contain Zn. 

Pour into an Erlenmeyer flask. Warm t< 
50°-60° and saturate with H 2 S. Cork and allow 
to stand 5-10 minutes. A white flocculent pre¬ 
cipitate is ZnS. In case of doubt confirm zinc 
by Co(N 0 3 ) 2 test, given below. 

Confirmation of Zinc.—Transfer the precipi-j 
tate to a filter and dissolve it by pouring repeat¬ 
edly over it 5-10 cc. HN0 3 (1.07). To the 
filtrate add 4-5 drops of N/100 Co(NOJ 2 ; 
evaporate almost to dryness to expel the acid: 
then neutralize with Na 2 C0 3 (10 per cent sol.), 
adding \ cc. in excess. Evaporate to dryness 
and ignite gently until the purple color of the 
cobalt disappears. Allow to cool. Agreencoloi 
is due to the presence of a double oxide of zinc 
and cobalt. 











THE METALS 


115 


Notes on the Analysis of the Ammonium Sulphide Group 
Procedure A 

Interfering Substances.—The oxalates and phosphates of the heavy metals 
e insoluble in neutral or alkaline solutions or in solutions containing weak 
ids such as acetic acid. Upon making the solution alkaline with NH 4 OH 
jr precipitation of (NH 4 ) 2 S Group, if oxalic acid and phosphoric acid are 
esent, Ca, Ba, Sr, and Mg will be precipitated as phosphates or oxalates, 
nee the removal of the acids is necessary. Since these salts are insoluble 
neutral or alkaline solutions, the acid radicals need not be looked for in 
lutions of salts that are readily soluble in hot water. Oxalates and tar- 
ites rarely occur in actual analysis of inorganic substances, so that a test 
r these is not generally made. If present, they may be removed by evaporat- 
jg the solution to dryness and igniting with ammonium nitrate. Organic 
mpounds may also entirely prevent the precipitation of the Iron Group, 
tiese substances are generally detected and removed in the preparation of 
ie solution. 

Test for Oxalate.—Add, drop by drop, 5-10 cc. of a hot solution of Na 2 C 03 
0 per cent) to a small portion of the H 2 S filtrate. Shake to mix well, and 

I low to stand for several minutes; filter if necessary. Then add a few cc. 
CaCl 2 solution. A white precipitate indicates the oxalate CaC20 4 . 

Test for Phosphate.—Strongly acidify a small portion of the solution with 
N0 3 (1.42), and pour it into four times its volume of ammonium molybdate 
lution. Warm to 60° or 70° for about 10 to 30 minutes. A fine yellow 
ecipitate indicates the presence of a phosphate. 

Removal of Phosphoric Acid.—The following reaction of phosphoric acid 
kes place with heavy metals in alkaline solutions: 

(NH 4 ) 2 S Group—H 3 PO 4 +FeCl 3 +3NH 4 OH = FePO 4 +3H 2 0+3NH 4 C1. 
(NH 4 ) 2 C0 3 Group—2H 3 P0 4 +3BaCl 2 +6NH 4 0H = 

Ba 3 (PO 4 ) 2 +6H 2 0 +6NH 4 C1. 

If phosphates are present, the acid radical should be removed as follows: 
Test one-tenth of the solution for iron by making alkaline with NH 4 OH 
precipitate the iron, then dissolving the precipitate in HC1 and adding a 
w drops of the filtrate to about 5 cc. of KCNS. A blood-red solution 
oves iron to be present. 

To the remainder of the solution add NH 4 OH until barely neutral. (A 
ght precipitate will form, which remains insoluble on shaking.) Now add 
;etic acid to acidity and about 5 cc. of ammonium acetate (50 per cent 

. 







116 


QUALITATIVE ANALYSIS 


solution). If the precipitate is not brownish red in color, add, drop by drop 
FeCl 3 until the red color is produced. Unless the iron is in excess, the pre 
cipitate of FeP0 4 will be yellowish white. To insure complete removal o 
the phosphoric acid an excess is added, but care should be taken not to add to 
much, as ferric phosphate is soluble in FeCl 3 . Add water until the volume i 
100 cc. and boil for 5 minutes in a 250 cc. flask. (Add more water if th 
precipitate is large.) Allow to settle and filter while hot. To the filtrah 
add 2 to 5 cc. more of the ammonium acetate to precipitate excess of iroi 
as basic ferric acetate. Boil and filter if a precipitate forms. 


Filtrate contains salts of (NH 4 ) 2 S and 
(NH 4 ) 2 C0 3 Groups, e.g., Co; Ni; Zn; Mn; 
Al; Cr; Ca; Ba; Sr; Mg. 

Pass in HoS uDon addition of NH 4 OH and 

Precipitate contains basi 
acetate, hydroxide, and phos 
phate of iron. Reject. 

NH 4 C1. 




Precipitate sulphides of 

(NHOaS Group. Analyze 
in usual way. 

Filtrate contains the salts of the (NH 4 ) 2 CO 
Group with magnesium. Use for the analysis 0 
these elements. 


Reaction of iron on phosphoric acid in presence of ammonium acetate.- 
FeCl 3 +H 3 PO 4 +3NH 4 C 2 H 3 0 2 = FePO 4 +3NH 4 C1+3HC 2 H 3 0 2 . Ammoniui 
acetate prevents formation of free HC1 which would dissolve FeP0 4 ; e.g 
FeCl 3 -f H 3 PO 4 = FePO 4 4-3HC1. 


Analysis.—Regarding the separation of the members of this group, severs 
methods are in use. The Sulphide and the Hydroxy-Sulphide methods her 
given are more generally used. The author gives precedence to the firs 
method, which in his opinion gives more reliable results. Although the secon 
method has the advantage of simplicity, yet difficulties are apt to arise unde 
certain circumstances. For example, manganese may precipitate with iror 
aluminum and chromium upon oxidation. Zinc may also be carried dow 
in the presence of an excess of chromium. Likewise, traces of Ni and C 
may be lost, due to the hydroxides carrying down the elements, when Fe, A 
or Cr are present in large amounts. 

I. Precipitation.—The removal of the H 2 S is necessary for the observatio 
of the precipitation of certain members of the group that are thrown down a 
hydroxides by ammonium hydroxide in the presence of NH 4 C1. Iron 









THE METALS 


117 


precipitated as grayish white, Fe(OH) 2 , changing to green and finally to 
brownish red, Fe(OH) 3 . Chromium precipitates as grayish green, Cr(OH) 3 ; 
aluminum as white, Al(OH) 3 . (In large quantities zinc precipitates as white, 
Zn(OH) 2 ; manganese as brown, Mn(OH) 2 ; cobalt as rose-red, Co(OH) 2 , 
changing to brown.) (The- rare elements may be found here, as white, 
Gl(OH) 2 ; white gelatinous, Th(OH) 4 ; white flocculent, Zr(OH) 4 ; white, 
.Ce 2 (OH) 5 ; white, La 2 (OH) : ; pale rose, Di 2 (OH):; white, Y 2 (OH) 6 ; white, 
Yb 2 (OH) : ; white, Se 2 (OH) e ; white, Er 2 (OH) 6 ; white, H 2 Ti0 3 ; white, 
Ta0 2 *0H; white, H 3 Nb0 4 ; yellow, (NH 4 ) 2 U 2 0 7 .) 

The monosulphide of ammonia is used in place of the polysulphide, as the 
latter dissolves NiS and adds sulphur to the precipitate, coloring the filtrate 
yellow. H 2 S is used in place of (NH 4 ) 2 S when nickel is present, as the sulphide 
of nickel dissolves slightly in the latter and scarcely at all in the gas. 

If HC1 is present in the solution, NH 4 C1 is formed. If not, this reagent 
should be added, as it prevents the precipitation of Mg(OH) 2 and renders 
Al(OH) 3 less soluble. 

A small amount of precipitate is apt to escape notice, owing to its trans¬ 
parency in case of fight-colored precipitates, hence care should be used before 
pronouncing the group absent. 

Ammonium sulphide precipitates white, ZnS; pink, MnS, oxidizing to 
brown, Mn 2 0 3 ; black, CoS; black, NiS; it changes the hydroxide of iron to 
black, FeS, but produces no change on the hydroxides of aluminum or 
chromium. 

(The sulphides of the rare elements, T1 2 S and U0 2 S, are dark brown. 
Ti, Be, Zr, remain as hydroxides.) 

The sulphide of nickel may dissolve slightly, coloring the filtrate yellowish 
brown This may be prevented by avoiding an excess of NH 4 OH and by 
precipitating the sulphides by H 2 S or by (NH 4 ) 2 S in a small Erlenmeyer 
flask, keeping the flask corked during intervals to prevent action of the air 
and by filtering rapidly, keeping the filter funnel covered by a watch glass 
between intervals of washing. NH 4 C1 prevents formation of soluble colloidal 
solutions, and H 2 S prevents oxidation. Hence these should be added to the 
wash water. If the filtrate is brown, make barely acid with acetic acid, boil 

and filter. . . , . , 

II. The separation of nickel and cobalt from the remaining elements of 
the group depends upon the comparative insolubility of NiS and CoS in cold 
2N • HC1, while the remaining precipitates dissolve. The corked flask is 
used as a precaution against the formation of sulphates by the oxidizing 

action of the air. „ 

III The borax bead tests may be conclusive for nickel or cobalt when 

existing alone, but if both are present, the intense blue of the cobalt compound 


118 QUALITATIVE ANALYSIS 

masks the color of that of nickel so that a separation has to be made in order 
to detect the latter. 

A. K 3 Co(N 0 2 ) 6 , although slightly soluble in water, is difficultly soluble 
in a concentrated solution of potassium nitrite, hence use excess of that 
reagent. The precipitation takes place slowly. Nickel will precipitate 
only in concentrated solutions. 

B. KCN in neutral solution first precipitates green, Ni(CN) 2 ; and dark 
brown, Co(CN) 2 . These dissolve in an excess of KCN, forming the soluble 
salts K 2 Ni(CN) 4 and K 4 Co(CN) 6 . NaBrO decomposes KCN, forming 
KCNO, which then oxidizes nickel to the nickelic state, whereupon it is 
precipitated as brownish black, Ni(OH) 3 by the NaOH formed in the solution. 

Cobalt, although already in the cobaltic state, is not precipitated because 
its complex ion, Co(CN)'"e, is not sufficiently ionized to react with NaOH 
to form the insoluble Co(OH) 3 , hence cobalt remains in solution. 

NaBrO is made by adding Br to a 10 per cent solution of NaOH until the 
solution is distinctly red and then adding half its volume of NaOH. As the 
reagent decomposes, it must be used fresh. NaOH and Br water may be 
used instead. The starch iodide test is used to show that an excess of the 
reagent has been added sufficient to destroy excess of KCN and to oxidize 
nickel to the nickelic state. 

In the final confirmation of nickel it must be remembered that the solu¬ 
tion must be saturated. The color will not appear until the solution is nearly 
saturated with hydrogen sulphide gas. 

In the precipitation of iron and manganese the peroxide is added in small 
portions at a time to a cold solution to prevent, as far as possible, its decom¬ 
position, which would take place with explosive violence from a hot solution. 
A steady evolution of oxygen shows that a sufficient quantity has been added. 
Chromium is oxidized to chromate, iron to Fe(OH) 3 , and manganese to Mn0 2 . 
The peroxide should be free from A1 and Si. 

IV. The insolubility of the manganese compound in nitric acid is taken 
advantage of in the separation of manganese from iron, Fe(OH) 3 being 
soluble. 

V. Cobalt and nickel may be precipitated with the manganese owing to 
their slight solubility in dilute HC1 and their reprecipitation by NaOH and 
Na 2 0 2 . Manganese when precipitated is first light colored, rapidly turning 
brown, due to oxidation. In case of doubt the confirmatory test may be 
made. 

Iron is recognized by its brownish red color as a hydroxide, manganese 
being a dark brown. The confirmation of iron is reliable if nitric acid is 
absent. The decomposition of KCNS by this reagent will cause a red 
color. 


THE METALS 


119 


VI. The solution contains aluminum, chromium, and zinc. Nitric acid 
is used in place of HC1 to prevent risk of reduction of chromic acid. 

The excess of NH 4 OH is added to keep the zinc in solution. A large excess 
would dissolve Al(OH) 3 . 

The reagents NaOH and Na 2 0 2 are apt to contain aluminum and silica as 
impurities. A blank test should be made to determine their purity. 

VII. The confirmation test for aluminum is made to guard against mistak¬ 
ing Si(0H) 2 0 for Al(OH) 3 . The former gelatinous substance does not dissolve 
in HNOs, whereas Al(OH) 3 will go into solution. In the cobalt test for alumi¬ 
num the latter element must be in excess for a satisfactory result. A second 
confirmation test is made as follows: Dissolve the hydroxide in HC1 (1.12), 
and add 1^ volumes of ether. Saturate the mixture with HC1 gas. A crystal¬ 
line, colorless precipitate is A1C1 3 *6H 2 0. 

The blue compound formed by the cobalt nitrate test is probably a double 
oxide of aluminum and cobalt, and may be Co(A10 2 ) 2 . An excess of cobalt 
would obscure the blue, owing to the formation of the black oxide of cobalt. 

VIII. A yellow-colored solution is generally an indication of the presence of 
chromium. In the confirmation test an excess of H 2 0 2 should be avoided, as 
it is apt to decompose the higher oxide of chromium, causing the test to fail. 

An immediate formation of a flocculent precipitate, upon the addition of 
H 2 S, is a characteristic test for zinc. Only one other sulphide of the group 
is light colored, e.g. MnS, but this is soluble in acetic acid. 

Pb0 2 test fails if chloride is present in the manganese precipitate. 




120 


QUALITATIVE ANALYSIS 


The Hydroxide-Sulphide Method of Separation 1 
Optional Method B 



If the solution contains H 2 S it should be expelled by boiling. Now add 
2-3 cc. HN0 3 (1.20) and again boil. (Filter if sulphur separates.) Now 
add 2-3 cc. NH 4 C1 (if HC1 is not already present) and add a slight excess of 
NH 4 OH; boil and filter at once. 


Precipitate.—Fe(OH) 3 , red; Cr(OH) 3 , green; Al(OH) 3 , 
white. Wash with hot water and dissolve in a few drops of 
HC1 (1.12). Transfer the cold solution to a casserole and 
add Na 2 0 2 in small quantities at a time until the mixture is 
strongly alkaline; boil to decompose excess of Na 2 0 2 , and 
filter. 


Residue.—Fe(OH) 3 . 
Dissolve in warm HC1 
(1.12), and test for Fe 
with K 4 Fe(CN) G or 
KCNS. With first re¬ 
agent a blue coloration 
is due to Fe 4 (Fe(CN) 6 ) 3 . 
A red color with KCNS 
is Fe(CNS) 3 . 


Solution.—Na 3 + A10 3 and 

Na 2 + Cr0 4 . Acidify with acetic 
acid and divide into two portions. 

(a) Add 
Pb(C 2 H 3 0 2 ) 2 . 

A yellow ppt. is 
PbCr0 4 . 

Confirm Cr by 
H 2 0 2 ether test. 

(b) Add 
NH 4 OH in 
slight excess and 
boil. A white, 
gelatinous pre¬ 
cipitate indi¬ 
cates aluminum. 

Confirm b y 
Co (NO 3 ) 2 test. 


Filtrate.— 

Co++Cl 2 -; 
Ni ++ Cl 2 -; 
Mn++Cl 2 -; 
Zn++Cl 2 -; . 
and may also con¬ 
tain the metals of 
the (NH 4 ) 2 C0 3 
and the Soluble 
Groups. Boil 
and pass in H 2 S 
through the hot 
solution until it 
smells strongly 
of the gas. Fil¬ 
ter and wash the 
precipitate with 
hot water con- 
taining a few 
drops of (NH 4 ) 2 S. 


Wash the precipitate into a beaker with dilute HC1 (1.035) and allow to stand 
5-10 minutes. (If the precipitate is not black, Co and Ni are absent. If this 
is the case, dissolve the residue in HC1 ( 1 . 12 ), and proceed at once to the 
analysis for manganese and zinc.) 


1 If chromium and zinc are both present, they are apt to precipitate each 
other in an ammoniacal solution. Manganese is also apt to precipitate when 
present in large amounts. In such case, separation of Al, Fe, and Cr as 
hydroxides is not satisfactory. 
















THE METALS 


121 


Residue may be CoS and NiS, black. 
Test for Co with borax bead; if present, 
the bead will be colored blue. If bead 
is brown, Ni is present. Since the blue 
color of the cobalt would mask the 
brown color of nickel, it is necessary to 
test for Ni. Positive tests for nickel 
and for cobalt may be found in the 
General Procedure A, Section III, page 
112 . 


Solution may contain Mn + + 
Cl 2 ~, Zn ++ Cl 2 ~ (trace of Ni). 
Boil to expel H 2 S and add an excess 
of NaOH; boil and filter. 


Precipitate.— 
Mn(OH) 2 (trace 
Ni(OH) 2 ). 

Confirm Mn. 

(а) Borax bead 
—O.F. amethyst 
purple. R.F. 
colorless. 

(б) Confirm by 
lead oxide 
method. (See 
Procedure A.) 


Filtrate.— 
Na 2 + Zn0 2 . 
Pass in H 2 S. A 
white precipitate 
indicates Zn. 

Confirm by ash 
test with cobalt 
nitrate. 

(See Procedure 
A.) 


Notes on Procedure B 

This method takes advantage of the fact that aluminum, chromium, and 
iron are precipitated as hydroxides in solutions made alkaline with NH 4 OH 
in the presence of NH 4 C1. 

The hydroxides of chromium and zinc are soluble in NaOH, whereas 
Fe(OH) 3 is insoluble, hence the latter may be removed from the former by 
the method given. 

In the removal of phosphoric acid, chromium and aluminum may be 
precipitated with the phosphate. They may be tested for by suspending 
the precipitate in water and adding Na 2 0 2 to strong alkalinity and filtering. 


Residue.—Fe(OH) 3 , etc. 


Filtrate.—Contains aluminum and chromium. 

-- Divide into two portions. Acidify one portion 

with acetic acid and add lead acetate. A yellow precipitate is PbCr0 4 . To 
the other portion add HC1 to acidity and then make alkaline with NH 4 OH 
and boil. A gelatinous, white precipitate is Al(OH) 3 . 












122 


QUALITATIVE ANALYSIS 


I. 


The Basic Acetate Method of Analysis of (NH 4 ) 2 S Group 
Optional Procedure C 


Oxidize the iron in filtrate of the H 2 S Group (from which H 2 S has been 
expelled by boiling) by boiling with 2-3 cc. HN0 3 (1.24). Add 5 cc. of NH 4 C1, 
if not already present; and then NH 4 OH until just alkaline.- (A slight pre¬ 
cipitate will form if Fe, Al, or Cr are present.) If iron is present, it can be 
recognized by the reddish color of the trace of precipitate that forms. If not 
reddish brown, dissolve in a few drops of HC1, add a little FeCl 3 solution 
and again neutralize. Now dissolve (if enough iron has been added) in a drop 
or so of HC1 and add ammonium acetate (10-15 cc. 4 N sol.); dilute with 
hot water to about 500 cc., boil and filter; wash free of acid with hot water. 


II. 


Precipitate.—Fe (OH) 2 C 2 H 3 O 2 ; A 1 ( 0 H) 2 C 2 H 30 2 ; Filtrate.—I o n s of 
Cr(0H)2C 2 H 3 0 2 . Iron has already been indicated. Ni, Co,Zn, Mn. See III. 
Divide into two portions (a) and (6). -—■ 


(a) Add 5-10 cc. H 2 0 and Na 2 0 2 in 
small portions. 

(6) Add 10 cc. NaOH and boil and 
filter. 

Residue.—Fe, reject. Filtrate.—Cr. 

Residue.—Fe, reject. Filtrate.—Al. 

Acidify the Na 2 Cr0 4 with acetic acid. 
A transient blue HCr0 4 indicates 
chromium. 

Confirm by evaporating to dryness 
and precipitating PbCr0 4 yellow in 
acetic acid solution. 

Acidify with HC1 (1.12), make just 
alkaline with NH 4 OH. A white floc- 
culent precipitate is due to Al(OH) 3 . 
Confirm by the Co(NO s ) 2 test. 

Blue residue is CoA10 2 . 


III. 


Filtrate from the Acetates of Al, Cr, and Fe.—Concentrate to about 
100 cc. Make just alkaline with NH 4 OH. Heat to boiling and add 5-10 cc. 
(NH 4 ) 2 S; filter, and wash with hot water containing a little H 2 S and NH 4 C1 
until free from alkali. 


Precipitate.—NiS, CoS, MnS, ZnS. Add 10-30 cc. Filtrate.—Ions of 
cold HC1 (1.12), digest, stirring thoroughly, filter, and the following groups, 
wash residue with water containing H 2 S.- 



















THE METALS 


123 


IV. 


Residue.—NiS, CoS. 
Test and separate ac¬ 
cording to methods 
already studied. 


Filtrate.—ZnCl 2 and MnCl 2 . Boil to expel H 2 S, 
make just alkaline with NaOH, shake and filter. 


Precipitate.— 

_Mn(OH) 2 , first light 

colored, changing to 
brown. (Ni and Co may be present.) 

Confirm.—Fuse in Pt loop with Na 2 COs. A dark- 
green bead is NaMn0 4 . (Light green may be due 
to Ni.) 


Filtrate.—Na 2 Zn0 2 .— 
Acidify with acetic acid 
and pass in H 2 S. A white 
ppt. is ZnS. 

Confirm with Co (NO 3 ) 2 
test. CoZn0 2 , green. 


Notes on Procedure 

Chromium is precipitated on boiling as the basic acetate only in 
presence of relatively large amounts of ferric iron and aluminum. If Cr 
is present in relatively large amount and Fe and A1 only in small amount 
the precipitation of the basic acetates is incomplete. 

The excess of Fe also removes any P0 4 that may be present. 

NiS is soluble in excess of NH 4 OH, hence this is avoided. 

NH 4 C1 prevents colloidal solutions forming. 

ZnS in acetic acid solution is less apt to be contaminated than in alkaline 
solution. 



if f 









124 


QUALITATIVE ANALYSIS 


CLASSROOM REVIEW 

1. What general substances interfere in the precipitation and separation 
of this group. Why? How may these be removed? 

2. What reactions are common to all the members of the Ammonium 
Sulphide Group? 

3. Make a comparative study of the general methods of analysis given. 
What are their relative merits? 

4. Devise another method for the separation of nickel from cobalt. 

5. Why are the carbonates and sulphides of ferric iron and of chromium 
and aluminum decomposed by water? 

6. (a) In what way do organic compounds interfere with the analysis of 
this group? 

(b) Why does the presence of the phosphate anion interfere? 

7. Why is not magnesium precipitated by ammonium hydroxide when 
ammonium chloride is present in the solution? 

8. Why does a solution of K 4 Fe(CN)6 fail to give the ordinary tests for 
iron? 

9. Be prepared to give reasons for each of the processes used in the separa¬ 
tion of the ions and the condition of the cations in the different stages they 
pass through before they are finally isolated and recognized. 

10. How are the sulphides of nickel and cobalt separated from the other 
members of the group? 

11. How are the hydroxides of manganese and iron separated? 

12. Could you use the Hydroxide Method B when aluminum is present 
in large amount and zinc in small amount, say in a ratio of 9 to 1. Give 
reason for your answer? 

13. How would you distinguish between ferrous and ferric iron? 

14. How would you distinguish a chromic salt from a chromate? 

15. What is the purpose of adding Na 2 0 2 in the first procedure A of 
separating the group? 

16. Write out the reactions involved in the course of analysis of a mixture 
containing the elements of this group; show the compounds formed with the 
addition of each reagent in the process of separation of the elements, e.g. 
trace the different phases an element passes through during its isolation and 
final identification, 


AMMONIUM CARBONATE GROUP 

Alkaline Earths, Group 4 

Common Elements.—Barium, Calcium, Strontium. 

General Characteristics. 

The group contains the alkaline earth metals, barium, calcium 
ind strontium, which are distinguished from the metals of preced- 
ng groups by the fact that their salts are not precipitated by 
3C1, H 2 S or (NfLj^S, and are distinguished from the metals 
)f the following groups by the fact their ions are precipitated as 
carbonates by ammonium carbonate in alkaline solutions in the 
Dresence of ammonium chloride. The elements are comparatively 
soft metals. They oxidize in the air, decompose water, forming 
lydroxides and liberating hydrogen. Their salts are similar. 
Most of these are white or colorless with exception of those whose 
icid radical imparts a color. The sulphides exist only in dry 
state; when treated with water H 2 S is evolved and the hydroxides 
Df the elements are formed. The members of the group are 
bivalent. 

Individual Characteristics. 

BARIUM 

Ba, at.wt. 137.37; sp.gr. 3.78; m.p. 850° C.; volatile at 950° C.; oxides, 

BaO, BaO a 

The metal is pale yellow. Its properties are similar to those of calcium 
and strontium. It is more readily oxidized in the air than either of its com¬ 
panion metals, and it decomposes water more readily. Its ores are not as 
common as those of calcium. It never occurs free in nature. The salts that 
are practically insoluble in water are BaSCh, BaCrC>4, BaCC>3, BaC 204 . 

The silicate BaSiF fl is slightly soluble. See list of compounds in Part V. 

125 





126 


QUALITATIVE ANALYSIS 


Solubility—Compounds of barium with the exception of the sulphate 
BaS0 4 , are soluble in hydrochloric and nitric acids. The sulphate is soluble 
in hot concentrated sulphuric acid, but is reprecipitated upon dilution of the 
solution. The sulphate is best fused with sodium carbonate, which trans¬ 
poses the compound to barium carbonate; sodium sulphate may now b< 
leached out with water and the residue, BaC0 3 , then dissolved in hydro 
chloric acid. 

DETECTION 

Preliminary Tests—Much time may be saved by making a preliminary 
test for barium, strontium, and calcium by means of the spectroscope anc 
avoiding unnecessary separations. By this means one-thousandth of a milli 
gram of barium, six hundred-thousandths of a milligram of strontium or cal 
cium may be detected. The characteristic spectra of these elements are giver 
in the chart, Plate I, Frontispiece. 

Barium is precipitated as the carbonate together with strontium and cal 
cium, by addition of ammonium hydroxide and ammonium carbonate to th< 
filtrate of the ammonium sulphide group. It is separated from strontiun 
and calcium by precipitation as yellow barium chromate, BaCr0 4 , from i 
slightly acetic acid solution. 

Saturated solutions of calcium or strontium sulphates precipitate white 
barium sulphate, BaS0 4 , from its chloride or nitrate or acetate solution 
barium sulphate being the least soluble of the alkaline earth sulphates. 

Soluble chromates precipitate yellow barium chromate from its neutra 
slightly acetic acid solution, insoluble in water, moderately soluble in chromi< 
acid, soluble in hydrochloric or nitric acid. 

Fluosilicic acid, H 2 SiF 6 , precipitates white, crystalline barium fluosilicate 
BaSiFe, sparingly soluble in acetic acid, insoluble in alcohol. (The fluosili 
cates of calcium and strontium are soluble.) 

Flame.—Barium compounds color the flame yellowish green, which appear; 
blue through green glass. 

Spectrum.—Three characteristic green bands (a, /3, 7 ). Faint bands als< 
in the red field of the spectrum. 

Barium sulphate is precipitated by addition of a soluble sulphate to a solu 
tion of a barium salt. The compound is extremely insoluble in water anc 
in dilute acids (soluble in hot concentrated sulphuric acid). The sulphate i; 
readily distinguished from lead sulphate by the fact that the latter is soluble 
in ammonium salts, whereas barium sulphate is practically insoluble. 


THE METALS 


127 


CALCIUM 

Ca, at.wt. 40.07; sp.gr. 1.5446 29 °; m.p. 810° C.; oxide, CaO 

The element is silvery white and harder than lead. It decomposes water, 
liberating hydrogen and forming calcium hydroxide. 

The following salts are practically insoluble in, water, CaC2C>4, CaC0 3 , 
CaF 2 , Ca 3 (P0 4 ) 2 . Their degree of solubility may be found in the list of 
calcium compounds given in Part V. 

The oxide, hydroxide, and salts of calcium are soluble in acids with the 
exception of gypsum and certain silicates which require fusion with sodium 
carbonate or bicarbonate followed by an hydrochloric acid extraction. 

DETECTION 

General Procedure.—In the usual course of qualitative and quantitative 
analysis calcium passes into the filtrates from the elements precipitated by 
hydrogen sulphide in acid and alkaline solutions (Ag, Hg', Hg", Pb, Cu, Cd, 
As, Sb, Sn, Fe, Cr, Al, Mn, Ni, Co, Zn, etc.), and is precipitated from an 
ammoniacal solution by ammonium carbonate as calcium carbonate, along 
with the carbonates of barium and strontium. The separation of calcium 
from barium and strontium is given on page 134. The oxalate of calcium 
is the least soluble of the alkaline-earth group. All, however, are soluble 
L mineral acids. Calcium oxalate may be precipitated from weak acetic acid 
solution by ammonium oxalate. 

Flame Test.—The flame of a Bunsen burner is colored yellowish red when 
a platinum wire containing calcium salt moistened with concentrated hydro- 
ohloric acid is held in the flame. 

Spectrum.—An intense orange and green line with a less distinct violet 
line. Note chart of the spectra of the alkaline earths. Plate I. 

STRONTIUM 

Sr, at.wt. 87.63; sp.gr. 2.64; m.p. 900° C; oxides SrO and Sr0 2 

Strontium is a soft yellow metal with properties very similar to those of 
barium and calcium. The metal occurs only in combined state in nature. 
Its minerals are not as abundant as those of calcium. 

i The salts SrC0 3 , SrC 2 0 4 , SrS0 4 are the least soluble of strontium salts. 
A. list of compounds may be found in Part V. 

DETECTION 

General Procedure.—Strontium is precipitated with barium and calcium, 
n the filtrate, from the ammonium sulphide group, by addition of ammonium 






128 


QUALITATIVE ANALYSIS 


carbonate to the ammoniacal solution. The precipitate is dissolved in acetic 
acid and treated with potassium dichromate, and the barium filtered off as 
BaCr0 4 . Strontium and calcium in the filtrate are separated from the excess 
of potassium chromate by reprecipitation as carbonates by the addition ol 
ammonium carbonate, the precipitates are dissolved in acetic acid and the 
excess of free acid neutralized with ammonia. Strontium may now be pre¬ 
cipitated from the concentrated solution by boiling with an equal volume of a 
saturated solution of calcium sulphate. 

Sodium Sulphate Test—A saturated solution of the salt added to a solu¬ 
tion containing strontium chloride, made strongly acid with acetic acid, anc 
the mixture boiled, will produce a distinct precipitate if strontium exceeds 
0.0015 normal. Calcium does not precipitate until 1.3 normahty is reached 

Flame Test.—Strontium, preferably in the form of the chloride, in a hydro¬ 
chloric acid solution, placed on a platinum loop and held in a colorless flame 
colors the flame crimson. (Lithium gives a red color, calcium a yellowish-red.. 
The test is best confirmed by means of the spectroscope. 

The Spectra of Strontium.—Eight bright bands; 6 are red, 1 orange, 1 blue 
Two of these, known as strontium /3 and 7, are red, the orange is strontium c 
and the blue strontium 8 . The delicacy of the test is 0.6 milligram Sr per cc 
The test is very much more delicate with the arc spectra, e.g., 0.03 milligran 
Sr per cc. 






THE METALS 


129 


LABORATORY EXERCISES 

Chemical Reactions of the Ammonium Carbonate Group 
BARIUM, Ba+ + 

A. Wet Tests. —Use BaCU solution for the tests. 

1. Precipitate BaC 03 from a solution made alkaline with 
NH 4 OH by adding (NEU^COa solution. 

Reaction. —BaCl 2 +(NH 4 ) 2 C0 3 = i BaC0 3 (white) +2NH 4 C1. 

2. Note that the precipitate is insoluble in NH 4 CI, but dis¬ 
solves in acetic acid. 

Reaction.— BaC0 3 +2HC 2 H 3 0 2 = Ba(C 2 H 3 0 2 ) 2 + T C0 2 +H 2 0. 

3. To the solution containing barium acetate add K 2 Cr 04 . 
rhe precipitate is BaCrCU, light yellow. What advantage can be 
;aken of the insolubility of the chromate of barium in acetic acid? 

Reaction— BaCl 2 +K 2 Cr0 4 = j BaCr0 4 (yellow) +2KC1. 

Note. —Chromates of calcium and strontium being soluble make it possible 
o separate barium from these elements by precipitation as BaCr0 4 and 
iltering off Sr and Ca. 

4. Filter off the precipitate and dissolve by adding a few drops 
>f dilute HC1, dilute with water and add half a cc. of dilute 
I 2 S04. The white precipitate is BaSCU. 

Reaction. —BaClj+H2S0 4 = BaS0 4 -f2HCl. 

5. To a fresh portion of the BaCU solution add a few drops 
f a saturated solution of CaSC>4. 

Reactions. —BaCl2+CaS0 4 = j BaS0 4 +CaCl2- 

6. To another portion add a saturated solution of SrSC>4. 

Reaction. —BaCl2+SrS0 4 = j BaS0 4 +SrCl2. 



130 


QUALITATIVE ANALYSIS 


The precipitate of BaSCU is a proof that it is less soluble than 
either CaSCU or SrSCU. 

7 . Barium sulphate is insoluble in alkalies, but boiled with a 
strong solution of Na2C03 the sulphate is partially transposed tc 
BaC03, the reaction being the reversible. 

Reaction.—BaS04+Na2C0 3 .<=^ 1 BaC0 3 +Na2SC>4. 

By fusing the sulphate of barium with several times its weight 
of sodium carbonate the transposition is complete. The sodium 
sulphate may be extracted with water and the residue, BaCC>3, 
then dissolved in dilute HC 1 . 

8 . Add ammonium oxalate reagent to another portion of 
BaCl2 solution. With barium exceeding 0.006 gram per 100 cc. 
of solution a white precipitation of BaC204 is obtained. 

BaCl 2 +(NH 4 ) 2 C 2 0 4 = i BaC 2 04 + 2 NH 4 Cl. 

9 . The precipitate is soluble in dilute mineral acids and in 
boiling acetic acid. (CaC204 is insoluble in hot acetic acid, SrC204 
sparingly soluble.) 

10 . Na2HP04 precipitates BaHP(>4 from neutral solutions and 
Ba3(P(>4)3 from ammoniacal solutions. The precipitate dissolves 
readily in acid solutions, including the weak acetic acid. 

Reactions.—(a) BaCl 2 +Na2HP0 4 = j BaHP0 4 +2NaCl. 

(6) 3 BaCl 2 + 2 Na 2 HP 04 -f 2 NH 4 OH = 
i Ba 3 (PO 4 ) 2 +4NaCl+2NH 4 C1+2H 2 0. 

B. Dry Tests. 11. Test a portion of solid BaCE with the 
flame test, first moistening the platinum wire used for the test with 
HC 1 . The color of the flame appears a light green. In presence 
of sodium the color appears a yellowish green. 

12 . Examine flame by means of the spectroscope. Note the 
colored chart Plate I for characteristic lines seen by means of 
the spectroscope. 



THE METALS 


131 


CALCIUM, Ca+ + 

A. Wet Tests.—Use CaCU for the tests. 

13. Add a few drops of NH 4 OH and then about 5-10 cc. 
»f (NH4)2CO3 solution. The precipitate is CaC(> 3 . 

Reaction.—CaCl 2 H-(NH 4 ) 2 C 03 = I CaC0 3 (white) +2NH 4 C1. 

14. Note the precipitate dissolves in dilute mineral acids and 
a acetic acid. 

15. Add 2 cc. NH 4 CI and heat to boiling. Does the pre- 
ipitate dissolve? 

16. Pour on a filter paper and dissolve the precipitate by pour- 
lg over it about 5 cc. hot acetic acid (30 per cent). To 2-3 cc. 
w 2 Cr 04 solution add several drops of the calcium acetate solution. 
)oes a precipitate form? 

Reaction.—CaC0 3 +2H.C 2 H 3 0 2 = Ca(C 2 H 3 0 2 ) 2 + T C0 2 +H 2 0. 

17. Now pour several drops of a fresh solution of CaCl2 into 
bout 5 cc. of NH4C2O4 solution. Does a precipitate form? 

Reaction.—CaCl 2 +(NH 4 ) 2 C 2 0 4 = j CaC 2 0 4 +2NH 4 Cl. 

18. Add a few drops of CaCU solution to a saturated solution 
f (NH4) 2SO4 and note whether a precipitate forms. 

From a concentrated solution, dilute H2SO4 or an alkali sul- 
hate, precipitates CaSCU, soluble on dilution, and appreciably 
|)luble in a hot concentrated solution of (NLU^SCU (distinction 
om Ba and Sr). 

19. Make another portion of the solution alkaline with NH 4 OH 
id precipitate the carbonate of calcium by the addition of 
j^H 4 ) 2 C 03 solution. Filter. Pour over the filter a few drops 
' HNO3 to dissolve the precipitate, catching the soluble nitrate 

an evaporating dish. Evaporate nearly to dryness and add 
-10 cc. of amyl alcohol; stir up with the residue and pour into 
(large test tube. Insert a thermometer and heat the solution to 
10°. Does the salt dissolve in the amyl alcohol? 





132 


QUALITATIVE ANALYSIS 


The solubility of calcium under this treatment is a methc 
of separation from strontium which remains as a residue < 
Sr(N 03)2 when the mixture is filtered. 

20. Dilute with an equal volume of ethyl alcohol and add 
few cc. of dilute H 2 S0 4 . The white precipitate is CaS0 4 . 

Reaction.—Ca(N0 3 ) 2 +H 2 S0 4 = J. CaS0 4 (white)+2HN0 3 . 

21. Disodium phosphate. The reaction is similar to that < 
Barium with this salt. 

B. Dry Tests. 22. Test a little of the solid CaCl 2 in the flan: 
and note color, dipping the test wire of platinum first in HC1. 

The flame is colored yellowish-red by the calcium salt. 

23. Examine the flame by means of a spectroscope and nol 
the spectrum of Ca. 

See colored chart for characteristic lines seen by means of tl 
spectroscope. 

STRONTIUM, Sr+ + 

A. Wet Tests. Use SrCl 2 solution for the tests. 

24. Make the same tests indicated for calcium. Note tht 
SrC 03 dissolves in HNO 3 , but the nitrate salt, formed upc 
evaporation, is insoluble in amyl alcohol. Pour the precipital 
on a filter. 

Reactions.—(a) SrCl 2 +(NH 4 ) 2 C0 3 = i SrC0 3 (white) +2NH 4 C1. 

(6) SrCO 3 +2HC 2 H 3 0 2 = f Sr(C 2 H 3 0 2 ) 2 + T C0 2 +H 2 0. 

(c) SrCl 2 +(NH 4 ) 2 C 2 0 4 = j SrC 2 0 4 +2NH 4 Cl. 

Note. —SrC 2 0 4 is only sparingly soluble in acetic acid, but dissolv 
readily in dilute mineral acids. (See Barium, Exp. 9.) 

25. Dissolve the precipitate in a few drops of water. To th 
solution add a few drops of a saturated solution of CaS0 4 . Tl 
white precipitate is SrS0 4 . 

Sr(N0 3 ) 2 +CaS0 4 = f SrS0 4 (white) +Ca(N0 3 ) 2 . 



THE METALS 


133 


Note. —SrS0 4 is practically insoluble in a strong solution of hot (NH 4 ) 2 S 04 . 
This affords a procedure for separating strontium from calcium, as the sulphate 
of the latter dissolves in strong hot solution of ammonium sulphate. The 
separation, however, is not complete, so that a confirmatory test is necessary. 

26. To another portion of SrCl 2 solution add a few drops of 
NH 4 OH and then K 2 Cr0 4 . Does a precipitate form? Now add 
4-5 cc. of ethyl alcohol. Does this cause a precipitate to form? 

The solubility of the chromate affords a method for separating 
strontium from barium. 

B. Dry Tests. 27. Test a portion of the strontium salt (solid) 
with the flame test. 

The platinum wire used for the test is dipped into HC1 and 
then into the salt to be examined. The flame is colored crimson 
or deep red by strontium salts. 

28. Examine the flame by means of the spectroscope. 

Consult the colored chart for the characteristic lines seen 
through the spectroscope. 

Table of Reactions 

Turn to the table of comparative reactions for the ammonium carbonate 
groups, making the tests indicated here, which have not been given under the 
exercises above. 



134 


QUALITATIVE ANALYSIS 


Outline of the Method of Separation and Detection of the 
Ammonium Carbonate Group 

By means of the flame test it is possible, with a little practice, 
to detect the members of this group. The characteristic colors 
do not appear at the same time owing to the difference in the 
volatility of the chlorides of barium, calcium and strontium. 
Examination of the flame by means of the spectroscope establishes 
with certainty traces of these elements in the solution examined. 
These tests are valuable for confirmation of these elements. 

A rapid preliminary examination of the solution may be made 
on three portions. The fact that SrSC>4 and BaSC >4 are less soluble 
than CaS 04 enables us to detect one or both of these elements 
by addition of a saturated solution of CaSC >4 to the concentrated 
solution of this group. The precipitate may consist of one or 
both of these sulphates. Should a precipitation occur, a second 
portion is examined for Ba and Sr by means of K 2 Cr 04 . BaCr 04 
will precip'tate and Sr may be found, if present, in the filtrate by 
precipitation with CaS 04 . Calcium is detected in a third portion 
by precipitation as CaC 2 C >4 after removal of the less soluble 
sulphates with H2SO4. 

In the general procedure if the solution examined is the filtrate 
from the ammonium sulphide group, a sufficient amount of NH 4 C1 
will be present to prevent precipitation of MgC0 3 with carbonates 
of Ba, Ca and Sr. In an original solution it will be necessary to 
add NH 4 CI. The members of the group are precipitated in 
presence of NH 4 C 1 by addition of (NH 4 ) 2 C0 3 to the ammoniacal 
solution containing the group. The alkalies, if present, are 
removed by filtration. The precipitate is dissolved in acetic acid 
and from the solution, diluted, BaCr 04 is precipitated by adding 
K2CrC>4. Calcium and strontium do not precipitate and will 
pass into the filtrate. To remove the excess K 2 Cr0 4 , CaC0 3 
and SrC0 3 are again precipitated. The carbonates washed free 
of the reagents are brought into solution as nitrates or acetates 







THE METALS 


135 


and detected by one of two optional methods given. The first 
procedure takes advantage of the insolubility of Sr(NOs )2 in 100 
per cent amyl alcohol Ca(NOs )2 being soluble a separation is 
effected. The elements are now confirmed. 

In the second procedure the carbonates of Ca and Sr are con¬ 
verted to the soluble acetates. SrS0 4 is precipitated by addition 
of a saturated solution of (NH 4 ) 2 S0 4 , calcium remaining in solu¬ 
tion. The sulphate of strontium may now be dissolved in HC1 
and the flame test made. CaC 2 0 4 is precipitated from an am- 
moniacal solution and further confirmed by testing its solubility 
in dilute acetic acid and by the flame test. 


Rapid Preliminary Examination for Barium, Strontium, and Calcium 

Make a mixture of the chloride solutions of barium, strontium, and cal¬ 
cium, using about 5 cc. of each. Divide into three portions, A, B , C. 


A. Calcium Sulphate 
test for Strontium and 
Barium. 

Add about four vol¬ 
umes of a saturated solu¬ 
tion of CaS0 4 to portion 
A. The precipitate con¬ 
sists of BaS0 4 and SrS0 4 . 
These sulphates are both 
less soluble than that of 
calcium. 


B. Detection of Ba¬ 
rium and Strontium in 
a mixture. 

Test A indicates the 
presence of strontium or 
barium or both. Test 
B is to detect each. Add 
to the solution a slight 
excess of K2Cr0 4 . A 
yellow precipitate indi¬ 
cates BaCr0 4 . Filter 
and add to the filtrate 
2-3 cc. of a saturated 
solution of CaS0 4 . A 
white precipitate indi¬ 
cates the presence of 
Strontium. 


C. Detection of Cal¬ 
cium in a mixture of the 
soluble salts of the group. 

Add a few drops of 
H 2 S0 4 as long as a pre¬ 
cipitate forms. Filter 
and to the filtrate add 
NH 4 OH to alkalinity 
and then a solution of 
(NH 4 ) 2 C 2 0 4 . A fine, 
white precipitate insolu¬ 
ble in dilute acetic acid 
is CaC 2 0 4 . 










136 


QUALITATIVE ANALYSIS 


Separation of the Ammonium Carbonate Group 

I. Acidulate the filtrate of the Ammonium Sulphide Group with HC1, and 
evaporate to 15-20 cc. (If previous groups have not been sought, add 5-10 
cc. of NH 4 C1 solution.) Filter if the solution is turbid to remove the free 
sulphur. To the clear solution add NH 4 OH, drop by drop, until the solution 
is alkaline. Heat to boiling and add to the hot solution (NH 4 ) 2 C 03 in small 
portions at a time as long as a precipitate continues to form (20-30 cc.) 
Keep the mixture hot for five minutes, then filter and wash with small portions 
of hot water. 


II. 


Filtrate may contain 
Mg++, Na+, K+, Li+, 
NH 4 + , acid radicals, traces 
of Ba++, Ca ++ , and 
Sr + + . 


Precipitate.—White,—CaC0 3 , BaC0 3 , SrC0 3 . 

Dissolve the precipitate on the filter by pouring 
over it 10-20 cc. hot acetic acid (30 per cent solu¬ 
tion). Repeat the operation with the filtrate if 
necessary. Test a small portion of the filtrate with 
K 2 Cr 04 . If a precipitate forms, add to the re- 
mainder of the solution about 5 cc. NaC 2 H 3 0 2 and then K 2 Cr0 4 , drop by 
drop, as long as a precipitate continues to form. The supernatant liquid 
should be slightly yellow to indicate an excess. Warm the solution. Allow 
the precipitate to settle and filter. (In case the blank test gives no precipi¬ 
tate, omit the addition of the chromate and proceed to the tests for strontium 
under IV.) 

III. 


Precipitate.—Light yellow, BaCr0 4 . Dissolve in dilute 
HC1 and add an equal volume of a saturated solution of 
SrSCL (any soluble sulphate will do). A white precipitate 
is BaS0 4 . Further confirmation may be made with flame 
and spectroscopic tests. 

treat with NH 4 OH and (NH 4 ) 2 C0 3 , as indicated above, 
the carbonate, boil, filter, and wash. 

IV.___ 

Precipitate.—SrC0 3 , CaC0 3 . 

Preliminary Test for Strontium.—Dissolve a small portion of the precipi¬ 
tate in a few drops of warm acetic acid and dilute to 5 cc. Test the strontium 
by adding a saturated solution of CaS0 4 . If no precipitate forms, test the 
remainder of the solution for calcium according to the procedure for calcium 
under Va or V6. If strontium is present, follow directions for separation 
under either Va or V6. 


Filtrate— Ca + + , 
Sr++, C 2 H 3 0 2 “, 

Cr0 4 —. 

Refilter if the 
solution is not clear. 
Boil the filtrate and 
Add 5 cc. more of 












THE METALS 


137 


Va Separation of Strontium and Calcium 


Dissolve the precipitate SrC0 3 and CaC0 3 in a few 
drops of dilute HN0 3 , and evaporate almost to dry¬ 
ness in a porcelain dish. (If Ba is absent (test under 
II), add 2 cc. cone. HN0 3 and evaporate to dryness to 
expel acetic acid; take up with a few drops of HN0 3 s 
10 cc. of amyl alcohol, stir and transfer to a test tube, 
eter. Boil until the temperature rises to 130°, ad 
replace that which evaporates if the volume decreases t 
through a dry filter. 

Filtrate. — Cr0 4 , 
C 2 H 3 0 2 — . Reject the 
solution. 

md reevaporate.) Add 
, and insert a thermom- 
ding more alcohol to 
;o less than half. Filter 

Residue.—Sr(N0 3 ) 2 . Rinse the residue 
into a test tube with absolute alcohol. De¬ 
cant the clear supernatant liquid through a 
filter into the solution to be tested for cal¬ 
cium. 

Confirm strontium by the flame and the 
spectroscope. 

The salt dissolved in a few drops of water 
and poured into a saturated solution of 
CaS0 4 will produce a white precipitate of 
SrS0 4 if the solution contains strontium. 

Solution.—Ca ++ 2N0 3 _ . 
Dilute with an equal volume of 
ethyl alcohol and add dilute 
H 2 S0 4 . A white, flocculent pre¬ 
cipitate, CaS0 4 , indicates Cal¬ 
cium. 

Confirm by flame and spec¬ 
troscopic tests. 

V b Optional Method for the Separation of Strontium and Calcium 

Dissolve the precipitate SrC0 3 and CaC0 3 in a few drops of warm acetic 
acid and dilute to 5 cc. Add a saturated solution of (NH 4 ) 2 S0 4 ; boil and 
filter . 1 

Precipitate.—SrSO 4 , 
white. Confirm by 
flame test, etc. 

Filtrate.—Ca ++ , etc. Make alkaline with NH 4 OH 
and add a solution of (NH 4 ) 2 C 2 0 4 . A white precipi¬ 
tate insoluble in acetic acid is CaC 2 0 4 . 2 Confirm by 
the flame test. 


1 1. Separation of the sulphates of strontium and calcium in a hot 
saturated solution of (NH 4)280 4 is not complete, since a little CaS0 4 

| remains with SrS0 4 and some SrS0 4 goes into solution with CaS0 4 , hence 
confirmatory tests are necessary. 

2 Solubility: CaC 2 0 4 -H 2 0 = 0.000554 gram per 100 cc. H 2 0. BaC 2 0 4 -H 2 0 
= 0.0093 gram- SrC 2 0 4 -H 2 0 = 0.0051 gram. MgC 2 0 4 ‘2H 2 0=0.07 gram. 














138 


QUALITATIVE ANALYSIS 


Notes on the Analysis of the Ammonium Carbonate Group 

I. On boiling the filtrate from the Ammonium Sulphide Group free sulphur 
will separate out and cause the solution to become turbid. Filtration will 
remove this. 

An excess of NH 4 C1 should be avoided, as it will not only dissolve mag¬ 
nesium salts, but also cause the carbonates of calcium, strontium, and barium 
to dissolve. If too much NH 4 C1 is present, the solution should be evaporated 
to dryness and heated to expel ammonium salts, the residue taken up with 
water, and the analysis made for the group. 

Boiling the solution renders the carbonates of the group less soluble by 
preventing the formation of the soluble bicarbonates. Allowing the solution 
to stand for five minutes lessens the possibility of the precipitate passing 
through the filter. (See Introduction.) 

Traces of calcium, strontium, and barium may pass into the Soluble Group 
solution. They should be tested for and removed before making the test 
for magnesium. 

II. By testing a portion of the filtrate containing the acetates it can be 
determined whether it is necessary to add potassium chromate to the solution. 
Since this has to be removed in order to separate the elements strontium and 
calcium by the method here given, time will be saved by avoiding its addition 
if barium is absent. A method of separating strontium from calcium in the 
presence of Cr0 4 anion is given by William C. Bray in The Journal of 
the American Chemical Society, June, 1909. His method of separation is 
practically as follows: The solution containing Ca ++ , Sr + +, and C 2 Hi0 2 - 
together with Cr0 4 is made alkaline with NH 4 OH with 2-3 cc. in 
excess, then diluted to 60 cc. and 50 cc. of 95 per cent alcohol added. 
Strontium separates as a chromate, while calcium passes into the filtrate. 

The addition of the chromate, drop by drop, in the precipitation of barium 
prevents the occlusion of calcium or strontium and insures the complete 
precipitation of barium. An excess of the reagent colors the solution yellow, 
showing that the precipitation is complete. 

III. The reprecipitation of the strontium and calcium as carbonates is for 
the purpose of removing the chromate radical. This section is omitted if the 
preliminary test proves barium to be absent; in which case K 2 Cr0 4 is not 
added. 

IV. The preliminary test may be made quickly, the time gained in avoid¬ 
ing an unnecessary procedure for separation in absence of strontium makes 
this test advisable. 

Va. In this method of separating strontium and calcium, advantage is taken 
of the insolubility of strontium nitrate in amyl alcohol and absolute ethyl 
alcohol. Since amyl alcohol is apt to contain water, which would dissolve 


THE METALS 


139 


the precipitate, the solution is heated to 130° to drive off the water. The 
alcohol boils at this temperature. The calcium salt is soluble in amyl alcohol. 

V6. The optional method takes advantage of the solubility of CaS0 4 in a 
strong solution of ammonium sulphate. Strontium is precipitated by this 
reagent as the sulphate, SrS0 4 . 

The flame and spectroscopic tests for strontium and calcium are necessary 
for confirmation. The platinum wire, used for making the tests, should 
impart no color to the flame when dipped in pure cone. HC1 and held in the 
flame. The wire may be cleaned by dipping in HC1 and holding in the flame 
repeatedly until the impurities have volatilized, the final acid treatment 
being with fresh acid. The acid should be poured in a dish for use in the flame 
tests; never insert the wire in the reagent bottle. 

Magnesium.—In the system of analysis of the group by W. C. Bray, 
magnesium is included in the group, being precipitated as a double ammonium 
magnesium carbonate from a cold solution containing an excess of ammonium 
. carbonate in the absence of ammonium chloride. Magnesium remains in 
the filtrate with calcium after the removal of barium and strontium as chro¬ 
mates. It is separated as follows: The strontium filtrate, is diluted to 250 cc. 
with water heated to boiling and about 50 cc. of ammonium oxalate added. 
Calcium precipitates as an oxalate, and is thus removed. Magnesium is 
precipitated from the solution, made alkaline with NH 4 OH by the addition 
of disodium phosphate. The addition of alcohol hastens precipitation, as it 
renders the precipitates less soluble, thus preventing a reverse reaction. (See 
Introduction.) 

CLASSROOM EXERCISES 

1 . Turn to the Table of Reactions in Part V, and from the solubilities of 
the salts devise another method of separating the members of the Ammonium 
Carbonate Group. 

2. What are the following substances: Plaster of Paris? Bleaching 
powder? Baryta water? Superphosphate of lime? Lime water? Barium 
peroxide? Heavy spar? Gypsum? Mortar? Lime and slaked lime? 

3. What use is made of the members of this group in pyrotechnics? 

4 . What reactions are common to the members of this group? 

5. Give a method by which each member of the group may be extracted 
from its mineral. 

6 . Trace the changes that take place with each element during the process 
j of analysis, writing out the equations representing the reactions that take 

place with the addition of each reagent. 

7. Why must ammonium chloride be present during the precipitation 
of the group? 

8 . Describe the procedure for making a flame test. 



SOLUBLE BASIC GROUP 

The Alkalies, Sodium Group, Group 5 

Common Elements.—Magnesium, Sodium, Potassium, Ammonium. 

Rare Metals.—Lithium, Caesium, Rubidium. 

General Characteristics. 

The members of this group derive their name from the fact 
that their ions, in the presence of ammonium chloride, do not 
form insoluble salts with any of the precipitating reagents thus 
far used, nor do they have a common precipitating anion. Nearly 
all their salts are soluble and readily ionized in solution. This 
fact prevents a satisfactory separation, as in case of the groups 
thus far studied. The solubility of magnesium salts places this 
element with the alkalies, although it is classed in the periodic 
table with the alkaline earths, and possesses characteristics more 
in common with that group—Ca, Sr, and Ba. Its hydroxide, 
carbonate and phosphate are insoluble in water, but dissolve 
in presence of NH 4 C1. The presence of NH 4 C1 prevents the 
precipitation of magnesium carbonate with the members of the 
ammonium carbonate group. Lithium, sodium, potassium, rubid¬ 
ium, caesium, and ammonium have common characteristics, 
being grouped together as the alkali metals. They do not occur 
free in nature. Their compounds are widely distributed in nature, 
occurring commonly in mineral or salt waters and in many rocks; 
only sodium and potassium, however, are abundant. The ele¬ 
ments are soft, light metals that are easily melted, their melting- 
points decreasing and their densities increasing with the rise of 
their atomic weights. The metals possess a silver lustre, and are 
easily tarnished in the air owing to oxidation. They readily 
decompose water, forming strongly basic hydroxides with the 

140 






THE METALS 


141 


liberation of hydrogen. They are all univalent (Mg bivalent). 
Their carbonates and phosphates are soluble in water (except 
MgC 0 3 in absence of NH 4 C1), whereas those of all other metals 
are but slightly or difficultly soluble. 

The estimation of potassium and sodium is required in the 
analysis of rocks, clays, soils, ashes of plants, waters, brines, 
saline deposits, salts of the alkalies, and in many technical prod¬ 
ucts. The determination of potassium is of special importance 
in the analysis of fertilizers. The estimation of lithium is desired 
in the analysis of lithium minerals frequently in mineral waters, 
occasionally in rocks, and in certain other special substances. The 
estimation of rubidium and caesium is seldom required. For the 
less common elements lithium, rubidium and caesium consult 
Part VI. 







142 


QUALITATIVE ANALYSIS 


Individual Characteristics. 

The common characteristics will be omitted in the following 
descriptions. 

MAGNESIUM 

Mg; at.wt. 24.32; sp.gr. 1.69-1.75; m.p. 651°; b.p. 1120° C.; oxide MgO 

Magnesium is a white metal having a lustre similar to that of metallk 
aluminum. The element decomposes hot water, forming magnesium hydrox¬ 
ide and the liberation hydrogen. It burns at red heat with a bright white 
light. It will combine with nitrogen at white heat. Unlike the other mem¬ 
bers, it does not oxidize in dry air. It is the hardest metal of the list, and can 
be molded, and is ductile and malleable. 

Magnesium is soluble in acids and is also attacked by the acid alkali car¬ 
bonates. It is soluble in ammonium salts. The oxide, hydroxide, and the 
salts of magnesium are soluble in acids. Combined in silicates, however, the 
substance requires fusion with alkali carbonates to bring it into solution. 

The insolubility of its phosphate in. an alkaline solution is used for its 
separation from the other members of the group. 

Among the less water soluble compounds are: magnesium—ammonium sul¬ 
phate, MgNH 4 P0 4 , • 6H 2 0 (0.01322) 1 ; ammonium arsenate, MgNH 4 • As0 4 • 6H 2 0 
(0.038); borate, Mg(B0 2 ) 2 -8H 2 0; carbonate, MgC0 3 (0.0106); fluoride, MgF 2 
(0.0087 180 ); hydroxide, Mg(OH) 2 (0.0009); oxalate, MgC 2 0 4 -2H 2 0 (0.07 16 °); 
oxide, MgO (0.00062); phosphate, Mg 3 (P0 4 ) 2 -4H 2 0 (0.0205); and pyrophos¬ 
phate, Mg 2 P 2 0/. 

DETECTION 

General Procedure.—In the usual course of analysis magnesium is found 
in the filtrate from the precipitated carbonates of barium, calcium, and stron¬ 
tium. Magnesium is precipitated as white magnesium ammonium phosphate, 
MgNH 4 P0 4 , by an alkali phosphate, Na 2 HP0 4 , NaNH 4 HP0 4 , etc., in pres¬ 
ence of ammonoum chloride and free ammonia. The precipitate forms 
slowly in a dilute solution. This is hastened by agitation and by rubbing 
the sides of the beaker during the stirring with a glass rod. Crystals soon 
appear on the sides of the beaker in the path of contact, and finally in the 
solution. 

Baryta or lime water added to a solution containing magnesium produces 
a white precipitate of magnesium hydroxide. 

Both the phosphate and the hydroxide of magnesium are soluble in acids. 

1 The figures in brackets represent the grams weight of the substance 
soluble in 100 cc. of cold water. 


THE METALS 


143 


AMMONIUM 

Ammonia. NH 3 ,m.w. 17.03; D. (air) 0.5971; sp.gr. liquid 0.6234; m.p. 
— 77.3 ; b.p. —38.5° C., Crit. temp. 130°; liquid at 0° with 4.2 atmospheres 
pressure. Commercial 28 per cent NH 3 , sp.gr. 0.90. 

The gas is very soluble in water, alcohol, ether, etc. It occurs combined 
with acids in the air, in rain water, and in mineral springs, in the soil, in 
carnallite, guano, urine, etc. It is easily formed from the animal or vegetable 
tissues by bacterial decomposition. 

A large number of compounds are known, most of these are soluble in 
cold water. Among the few which are not easily soluble the following are 
more common: ammonium antimonate, NH 4 Sb0 3 -2H 2 0, bromo platinate, 
(NH 4 ) 2 PtBr 6 , (0.59 20 °) red; chloroiridate, (NH 4 ) 2 IrCl 6 (0.7 14 °) reddish 
,brown; chloroplatinate, (NH 4 ) 2 PtCl6 (0.67 20 °) yellow; metavanadate, 
NH 4 V0 3 , white, (slightly soluble in H 2 0, insoluble in presence of NH 4 C1); 
phosphomolybdate, (NH 4 ) 3 P0 4 -12Mo0 3 -3H 2 0 (0.03 15 °) yellow. The am¬ 
monium radical NH 4 acts as an univalent cation combining with the acid 
'adicals. 


DETECTION 

Ammonia. —Free ammonia is readily recognized by its characteristic odor. 
A glass rod dipped in hydrochloric acid and held in fumes of ammonia produces 
i white cloud of-ammonium chloride, NH 4 C1. 

Moist red litmus paper is turned blue by ammonia. Upon heating the 
|>aper the red color is restored, upon volatilization of ammonia (distinction 
Irom fixed alkalies). 

Nessler’s Test. 1 —Nessler’s reagent added to a solution containing am- 
aonia, combined or free, produces a brown precipitate, NHg 2 IH 2 0. If the 
.mmoniacal solution is sufficiently dilute a yellow or reddish-brown color is 
•roduced, according to the amount of ammonia present. The reaction is 
sed in determining ammonia in water. 

Salts of ammonia are decomposed by heating their solutions with a strong 
rase such as the hydroxides of the fixed alkalies or the alkaline earths. The 
dor of ammonia may now be detected. 

1 The reagent is made by dissolving 20 grams of potassium iodide in 50 
ta. of water, adding 32 grams of mercuric iodide and diluting to 200 cc. To 
jiis is added a solution of potassium hydroxide—134 grams KOH per 260 
h. H 2 0. 




144 


QUALITATIVE ANALYSIS 


POTASSIUM 

Potassium, K, at.wt. 39.10; sp.gr. 0.875; m.p. 62.5°; b.p. 757.5° C.; oxides 

K2O, IC2O4. 

The element closely resembles sodium. It occurs as a chloride and sul¬ 
phate in sea water and mineral springs; also in large deposits, generally 
above rock salt (Stassfurt deposits in Germany). Potassium is the most 
essential and least variable of all elements found in plant ash. 

A large number of compounds are known. The salts are generally soluble 
in cold water. Among the exceptions are the following: Potassium-anti- 
monate, KSb0 3 ; cobaltinitrite, 2 Co(N 02 ) 3 , 6 KN 02 - 3 H 2 0 (0.09) yellow; 
chloroplatinate K 2 PtClo (0.48 2 °) yellow; thioplatinate, K 2 Pt 4 S 6 ; bluish 
gray cryst.; uranate, K 2 U0 4 , orange yellow. The presence of alcohol 
decreases the solubility of the salts. See list of compounds in Part V. 

• 

DETECTION 

For the detection of potassium in insoluble compounds, bring the sample 
into solution by one of the methods given under preparation of the solution 
under Detection of the Metals, Part IV. In other cases, prepare a strong 
solution of the material to be tested. Where only very small amounts of 
potassium are present, remove all the constituents from the solution except 
the chlorides of magnesium and the alkalies by precipitation as sulphides, 
hydroxides and carbonates. In the presence of considerable amounts of 
potassium, small quantities of other constituents will not materially interfere 
with the flame and spectroscopic tests. After acidifying with hydrochloric 
acid, bring a drop of the solution to be tested into the non-luminous 
flame and observe the color produced through a blue color screen. In the 
presence of potassium, a distinct reddish-violet coloration will be apparent. 
This must not by confused with the color caused by large amounts of sodium, 
which appears bluish-violet through the screen. Comparison with the colora¬ 
tion produced by pure salts is advisable. If necessary, confirm the results 
by examining the flame in the spectroscope. In the presence of a moderate 
amount of a volatile potassium compound, a bright red line will be readily 
seen in the red portion of the spectrum, and a less distinct violet line will be 
visible in the violet field, 




THE METALS 


145 


SODIUM 

Sodium, Na, at.wt. 23.00; sp.gr. 0.9736; m.p. 97.6°; b.p. 877.6°C.; oxides 

Na 2 0, Na 2 0 2 . 

The metal is insoluble in kerosene and benzene. Sodium is the most 
ividely distributed element of the group. It occurs as a chloride in enormous 
leposits as rock salt. It occurs in mineral water, sea water, springs, and 
akes. 

Among the large number of sodium compounds a few only are difficultly 
soluble in cold water. Of these the following are worthy of note: Sodium- 
mtimonate, 2NaSb0 3 -7H 2 0 (0.031 120 ); pyroantimonate, Na 2 H 2 Sb 2 0 7 *H 2 0; 
limolybdate, Na 2 Mo 2 07 j uranate, Na 2 U 04 , yellow. See compounds in Part V. 

DETECTION 

Sodium is usually identified by the color which it imparts to the flame or by 

I neans of the spectroscope. The solution is prepared as directed under Prep- 
iration and Solution for Metals, Part IV, and is freed from all constituents 
>ther than the chlorides of magnesium and the alkalies by removal of these as 
ulphides, hydroxides and carbonates by the standard procedure. With 
ixceedingly small amounts of sodium, it may be necessary to remove the 
nagnesium also. After acidifying with hydrochloric acid, a drop of the 
olution is brought into the flame by means of a loop of platinum wire. In 
he presence of sodium, the flame assumes an intense yellow color, which is 
isually sufficient to identify the element. The results may be confirmed by 
jxamining the flame in the spectroscope, when the characteristic yellow 
odium line will be prominent even in the presence of traces of sodium. As 
, matter of fact, the ever-presence of the sodium line is a hindrance to the 
iuccess of the method, but by observing the sudden change in the intensity 
f the line, little trouble will be experienced in detecting exceedingly small 
mounts of the metal. 

Sodium may also be detected by precipitation as sodium pyroantimonate, 
Ta 2 H 2 Sb 2 0;-H 2 0, from a sufficiently concentrated neutral or weakly alkaline 
olution by means of a solution of acid potassium pyroantimonate. The 
recipitate comes down in granular or crystalline form, and its formation is 
astened by rubbing the sides of the vessel with a glass rod. In making this 
est, magnesium must be previously removed from the solution. 

In waters and soluble salts, it is usually sufficient to test directly the con- 
entrated solution in the flame or spectroscope. 




146 


QUALITATIVE ANALYSIS 


LABORATORY EXERCISES 

Chemical Reactions of the Soluble Basic Group 

Make the tests for the alkalies with concentrated solutions oi 
their chlorides. For the flame and spectroscopic tests use a little 
of the solid dissolved in HC1. The platinum wire should be clean. 
See Introduction, also Dry Tests in Part IV. 

MAGNESIUM * 

Use a solution of MgCl 2 or Mg(NOs) 2 . 

1 . Make a portion alkaline with a few drops of NH 4 OH and 
add a solution of (NH^COa. The precipitate is a double salt 
of magnesium ammonium carbonate. 

Reactions.—(a) MgCl 2 +2NH 4 OH = | Mg(OH) 2 (white) +2NH 4 C1. 

(6) 4MgCl 2 +4(NH 4 ) 2 C0 3 +H 2 0 = j Mg 4 (C0 3 ) 3 (0H) 2 + t C0 2 +8NH 4 C1. 

2 . Now add a few drops of NH 4 CI and heat the solution. Does 
the precipitate dissolve? 

Reaction.—Mg(OH) 2 +2NH 4 Cl+2NH 3 = Mg(NH 3 ) 4 Cl 2 (solution) +2H 2 0. 

3. Try the same test, beginning with a neutral solution in 
place of a solution made alkaline with NH4OH. 

Write out reaction. 

4. To another portion add NH 4 OH to alkalinity, and a few 
drops of NH 4 CI and then 2-3 cc. of Na 2 HP0 4 solution. The 
precipitate is MgNH 4 P0 4 . Does the addition of alcohol hasten 
precipitation? Does stirring with a glass rod hasten precipitation 

Reaction. MgCl 2 +Na 2 HP0 4 +NH 4 0H = [ NH 4 MgP0 4 (white cryst. 

+2NaCl 2 +H 2 0. 

Note .—Neutral solution Na 2 HP0 4 precipitates flocculent MgHP0 4 . 

Reaction.—MgCl 2 -fNa 2 HP0 4 = j MgHP0 4 (white flocc.)-f-2NaCl. 




THE METALS 


147 


5. Add to another portion Ba(0H)2. The white precipitate 
is .Mg(OH) 2 . 

Reaction.— MgCl 2 +Ba(OH) 2 = | Mg(OH) 2 +BaCl 2 . 

AMMONIA 

6 . In analysis, the original substance or solution is used. For 
the preliminary test use either solid NH 4 C1 or its solution. (Any 
ammonium salt will do.) Place in a test tube and pour on material 
2-3 cc. of NaOH and warm. An odor of ammonia can readily 
be detected. Moist red litmus paper held over the mouth of 
the tube will be turned blue. Care should be taken not to con¬ 
taminate the sides of the tube with the strong base. If the change 
af color is due to ammonia, the red color can be restored by heating 
the paper to drive off ammonia. 

7. Precipitation test with H 2 PtCl 6 . Chloroplatinic acid pre- 
3 ipitates a yellow crystalline compound (NH 4 ) 2 PtCl 6 . The salt 
's similar to that of potassium, from which it may be distinguished 
Dy heating with NaOH, the odor of NH 3 becoming evident. 

8 . Cobaltinitrite produces a yellowish precipitate with con¬ 
centrated solutions of ammonium salts, similar to the potassium 
'salt formed by this reagent. 

POTASSIUM 

Use a concentrated solution of KC1. 

9. To about 5 cc. add 2-3 drops of acetic acid, and then an 
?qual volume of sodium cobaltinitrite. If no precipitate forms 
mmediately, allow to stand 15 or 20 minutes. A yellow pre¬ 
cipitate is K 3 Co(N 0 2 ) 6 +water of crystallization. 

Note .—The test cannot be applied in the presence of ammonium salts, 
ince NH 4 yields a similar precipitate. 

10 . H 2 PtCl 6 precipitates yellow, K 2 PtCl 6 from neutral solu- 
ions, or concentrated acid solutions of potassium salts. See 
imilar test for ammonia. 



148 


QUALITATIVE ANALYSIS 


Compare solubilities of the potassium cobaltinitrite and chloroplatinah 
salts. It is evident that precipitation in the first form is a more sensitive 
test for potassium. See list of compounds in Part V. 

11 . Make the flame test with a small amount of the salt. Ex¬ 
amine through the same thickness of blue glass used in the 
sodium test. What advantage can be taken of this test? 

SODIUM 

Use a concentrated solution of NaCl. 

12. To a portion placed in a test tube, the solution being neu¬ 
tral or slightly alkaline, add an equal volume of dipotassiuir 
dihydrogen pyroantimonate (K 2 H 2 Sb 207 ), shake vigorously anc 
allow to stand some time. The white crystalline precipitate is 
Na 2 H 2 Sb 2 0 7 H 2 0. 

Note .—The solution must not be acid, as this would decompose the reagent, 
causing the precipitation of pyroantimonic acid. 

Reactions.—(a) 2NaCl+K 2 H 2 Sb 2 0, =1 Na 2 H 2 Sb 2 0 7 (white) +2KC1. 

(6) Acid on reagent—K 2 H 2 Sb 2 0 7 +2HCl =1 H 4 Sb 2 0 7 (white) +2KC1. 

Removal of other metals (except NH 4 and K) is necessary, since thest 
yield precipitates with the reagent. 

13. Make a flame test with a portion of the solution or use 
the solid salt with a few drops of HC1. Now examine the flame 
through a blue glass. If the glass is of proper density, the yellow 
rays will be entirely absorbed. Several thicknesses of glass ma> 
be necessary to cut out the rays. 

14. Examine the spectrum of sodium. 

For the less common elements, lithium, caesium, rubidium, set 
Part VI. 





THE METALS 


149 


Outline of the Method for Detecting the Soluble Group Metals 

Direct tests may be made for members of this group in presence 
of one another so that it is not necessary to effect a complete 
separation as in case of previous groups. Since Na 2 HP 04 pre¬ 
cipitates the alkaline earth metals the removal of these is necessary 
for a reliable test for magnesium, since the carbonates of Ba, Ca 
and Sr are slightly soluble and small amounts pass into the filtrate 
containing the soluble group. This removal is accomplished 
on one-third portion of the solution by adding (NH 4 ) 2 C 204 and 
(NH 4 ) 2 S0 4 , boiling and filtrating off the precipitated alkaline 
! earths. The concentrated filtrate is tested for magnesium. The 
remaining two-thirds of the original solution is evaporated to 
dryness and heated to expel the accumulated ammonium salts, 
which interfere in the detection of potassium on account of the 
similarity of ammonium compounds that would form with 
reagents used. These salts are volatilized at a temperature 
where practically no loss by volatilization of the alkalies occurs. 
Tests for sodium and potassium are made in separate portions. 

Ammonia is looked for in the original sample for the obvious 
reason that reagents containing this compound are used in the 
course of analysis. 




150 


QUALITATIVE ANALYSIS 


Analysis of the Soluble Basic Group 

Preparation of Solution 

Divide the filtrate from the Ammonium Carbonate Group into two por¬ 
tions: A, one-third, and B, two-thirds. Test portion A for magnesium, and 
meantime evaporate portion B to small bulk on a sand bath and finally to 
dryness on a water bath, and proceed as indicated in B, below. 

Removal of the Alkaline Earth Metals 

A. Before proceeding to the test for magnesium, traces of the previous 
group must be removed from the solution. In order to detect the presence 
of these add a few drops of the solution to about 2-5 cc. of a strong solution 
of (NH 4 ) 2 S 04 ; a slight turbidity indicates the presence of strontium or 
barium or both. To detect the presence of calcium add one or two cc. of the 
solution to an equal volume of (NH 4 ) 2 C 2 0 4 ; a slight turbidity is due to the 
formation of CaC 2 0 4 . If the tests indicate Sr, Ba, or Ca, add to the remainder 
of the portion A the reagents effecting their precipitation, and filter. 

Detection of Magnesium 

Residue.—Reject. Solution contains magnesium and the alkalies. Con¬ 
centrate the solution to about 5 cc. (Filter off any precipitate that may form.) 
To the filtrate add 1-5 cc. (NH 4 ) 2 HP0 4 solution and stir with a glass rod. 
A white, crystalline precipitate forming slowly, crystallizing in streaks wherever 
the rod has touched the beaker, proves the presence of Magnesium. (The 
solution should be made alkaline with NH 4 OH before the addition of 
(NH 4 ) 2 HP0 4 , if not already so.) 

Confirmation of MgNH 4 P0 4 .—Dissolve the precipitate in a little acetic 
acid. To the clear filtrate add NH 4 OH to make the solution alkaline. Stir 
vigorously and allow to stand. MgNH 4 P0 4 is again precipitated. 

Separation of the Alkalies—Potassium, Sodium and Lithium 

B. (a) Procedure in Presence of Magnesium and the Alkaline Earths. —To 
remove magnesium expel the ammonium salts by heating the residue obtained, 
by evaporation, to a temperature below dull redness until no more white fumes 
are driven off. (Hood.) Heat the sides of the dish as well as the bottom. 
Dissolve the residue in about 5 cc. of water and add Ba(OH) 2 , drop by drop, 
until no further precipitation occurs. The precipitate is Mg(OH) 2 . Filter, 
rejecting the residue. To the filtrate add a few drops of (NH 4 ) 2 S0 4 to remove 


THE METALS 


151 


barium. When the precipitation is complete add several drops of (NH 4 ) 2 C 2 O 4 
and filter. Reject the precipitate. (Ba, Sr, Ca.) Evaporate the solution 
to dryness, 

(6) Procedure after the Removal of Magnesium and the Alkaline Earths .—Expel 
the ammonium salts by heating in a hood to a temperature below dull redness 
until no more white fumes are driven off. (Heat sides as well as the bottom 
of the dish.) Add about 10 cc. of water containing a few drops of HC1 (1.12), 
warm and filter, and again evaporate the filtrate to dryness. Take up the 
residue with 5-10 cc. of water. Filter if not clear. Divide into two portions. 
I and II. 


Portion I.—Add a few drops of 
acetic acid if the solution is not 
already acid, and an equal volume of 
Na 3 Co(N0 2 ) 6 . Allow to stand 10 to 
20 minutes if a precipitate does not 
form readily. A yellow precipitate is 
K 3 Co(N0 2 ) 6 +aq., best seen on filter 
paper upon removal of the reagent 
by washing. Filter and wash residue 
with water, a few drops at a time. 

Potassium may also be detected by 
precipitation as K 2 PtCl6. See Chemi¬ 
cal Reactions, page 147. 

Confirm.—Dissolve residue in a 
little hot HC1 (1.12). Evaporate to a 
few drops and test the concentrated 
solution in the flame, cutting out the 
yellow rays by blue glass of sufficient 
density. A violet red color indicates 
potassium. Examine by spectro¬ 
scope. A flame violet-red giving a 
red and a blue fine proves Potassium. 


Portion H.—If the solution reacts 
acid, make neutral by the addition of 
a drop or so of KOH. Evaporate to 
about 1 cc., cool, and add 1 to 2 cc. 
K 2 H 2 Sb 207 ; pour into a test tube and 
allow to stand for some time (at least 
half an hour or longer). A white crys¬ 
talline precipitate is Na 2 H 2 Sb 207 H 2 0 . 

Confirm.—Decant off the solution. 
Wash the precipitate by adding small 
amounts of water at a time Test the 
residue in the flame, upon the addition 
of a drop or so of HC1 to bring it into 
solution. A brilliant yellow flame 
proves the presence of Sodium. Ex¬ 
amine the flame by means of the spec¬ 
troscope to detect the presence of 
Lithium. 


Ammonium.— Test original substance or solution by warming with a little 
aOH. Odor of ammonia. See tests for ammonia under the characteristic 

' Moist red litmus paper is colored blue by NH 3 . In warming the paper 
le NHs is volatilized and the red color restored. (Distinction from the other 

ikalies.) 









152 


QUALITATIVE ANALYSIS 


Notes on the Analysis of the Soluble Basic Group 

Test for Magnesium.—Since the phosphates of the alkaline earths are all 
insoluble in alkaline solutions, calcium, barium, and strontium must be 
removed completely from the solution before making the test for magnesium. 

Evaporation.—Ammonium salts must be expelled, since they may be 
mistaken for potassium. The residue is not heated to redness, as the alkali 
chlorides will volatilize when highly heated. 

Precipitation. —The residue obtained upon the expulsion of the ammonium 
salts may be tested directly by flame and spectroscopic tests by dissolving it in 
a few drops of HC1. The difficulty lies principally in the detection of potassium 
in the presence of sodium. A blue glass of sufficient density to cut out the 
yellow rays of sodium should be used. Again the fact that sodium is always 
present in the reagents and in the air makes the direct flame test unsatisfactory, 
as a yellow color will always be obtained with the residue, hence the advis¬ 
ability of using the precipitation test, since these traces will not respond to 
this test. For satisfactory results great care must be used. 

In the precipitation of potassium by cobalt nitric solution, if an excess of 
sodium is present, the potassium comes down as K 2 NaCo(N0 2 )6*H 2 0. 

Reagents. Sodium Cobaltinitrite. —Dissolve 100 grams of NaN0 2 in 200 cc. 
of water, add 60 cc. acetic acid (30 per cent) and 10 grams of Co(N0 3 ) 2 *6H 2 0. 
Allow to stand for two or three days; filter and dilute to 400 cc. 

Dipotassium Dihydrogen Pyroantimonate. —Dissolve 2 grams of the best 
commercial salt, K 2 H 2 Sb 2 0 7 ,in 100 cc. of boiling water and boil the solution for 
about a minute, cool quickly and add 3 cc. KOH (10 per cent) and filter. 

Test for Potassium. —The solution must not be alkaline when the reagent is 
added, since Co(OH) 3 would precipitate as soon as Na 3 Co(N0 2 ) 6 is added to 
alklaine solutions, hence the addition of acetic acid. 

Test for Sodium is made from neutral solutions, as Na 2 H 2 Sb 2 0 7 is soluble in 
an acid solution. The salt is a heavy crystalline precipitate, which may 
require some time for complete precipitation. The precipitate due to the 
presence of lithium is similar to that of sodium. The flame and spectroscopic j 
tests serve as a ready method of distinction, since lithium gives a carmine-red 
flame, and has in its spectrum a red and a feeble orange line. A fleeting 
yellow color should not be taken as evidence of the presence of sodium. 

For a method of determination of lithium the student is referred to a paper 
by W. C. Bray, The Journal of the American Chemical Society , June, 1909. 
His method is to precipitate lithium as a phosphate from an alcoholic solution 
containing the alkalies. 

Test for Ammonia is made with the original solution or solid, since during 
the process of analysis this substance has been added as a reagent in both the 




THE METALS 


153 


Ammonium Sulphide and Ammonium Carbonate Groups. It is not necessary 
to dissolve the sample, as the test may be made of the solid substance. 

CLASSROOM EXERCISES 

1. What substances are present in an ionized solution of NH 4 OH, NaCl, 
KOH? The student must remember that complete ionization does not take 
place. (See Introduction.) 

2. What impurities are found in common salt? How is it purified? 

3. What metal is removed from the other members of the group by 
precipitation? 

4. Why is it necessary to test for ammonia in the original sample? 

5. What precautions are observed in testing for magnesium? 

6. Why is it necessary to remove ammonia before testing for potassium? 

7. What metals have been examined by means of the spectroscope? 
What elements have been discovered by this means? 

8. Write out all reactions involved in the analysis of the members of this 
group. 


GENERAL REVIEW OF THE METALS 

1. Study the table outlining the procedure for separation of the basic 
elements given on page 230. 

2. Outline the procedure for separation and detection of silver, copper, 
tin, zinc and magnesium in a mixture of their chlorides. 

3. A white compound is given for analysis. This is insoluble in cold water, 
but goes into solution when heated. On cooling, crystals are formed. K 2 Cr0 4 
added produces a yellow precipitate—what is the compound? 

4. Review the tables of reactions in Part V. 

5. How would you distinguish between: 

(а) Antimony and arsenic in a mixture of the two? 

(б) Antimony and bismuth chlorides? 

(c) Ferrous and ferric iron? 

(d) Lead sulphate and barium sulphate? 

(e) Copper chloride and nickel chloride? 

(/) Chromic salt and a soluble chromate? 

(g) Magnesium chloride and zinc chloride? 


PART III 


THE ACIDS 


General Characteristics. 

Acids are electrolytes containing the common cation H + , which 
may be replaced by metals, forming salts. The chemical activity 
of acids depends upon their degree of ionization. Analysis of acids 
is the identification of the negative ion or the anion. This can be 
accomplished by testing directly for the radical. Although it is 
impossible to analyze acids by a process of elimination such as was 
used in the case with the metals, yet, by means of certain general 
tests or preliminary reactions, it is possible to recognize many of 
the acids, which can be further confirmed by special tests. Only a 
few anions need be looked for in an ordinary analysis, since the 
presence of certain metals in the solution proves the absence of 
certain acids. For example, if silver has been found in a solution 
soluble in water, chloride, bromide, and iodide anions are absent, 
since they would combine with silver to form insoluble salts; like¬ 
wise, a sulphate cannot be found in a water solution containing 
barium or lead, nor an oxalate in a neutral solution containing 
calcium. Furthermore the presence of certain metals furnishes a 
clue to the presence of certain acid radicals, generally associated 
with these metals. The tests for acids, therefore, follows the 
analysis of the metals. 

Classification. 

Acids may be classed under two major heads—Inorganic and 
Organic. The latter includes a very large number of acids, only a 
few of which concern us in our present course. The general char¬ 
acteristic of organic acids is their readiness to decompose when 
Heated, leaving a black residue of carbon (charring). 

154 


THE ACIDS 


155 


Acids are frequently classed under three general groups, based 
on the solubility of their salts. A number, for example, form in¬ 
soluble salts in an acid solution with silver nitrate, others form 
insoluble salts in a neutral solution with barium chloride, and a 
third class remains in solution in the presence of either or both 
of these reagents. The fact that certain acids volatilize or decom¬ 
pose under the influence of free dilute acids, such as nitric, hydro¬ 
chloric, or sulphuric, and the organic acids char when heated, 
has led us to include two additional groups as a matter of conveni¬ 
ence in our study of the individual properties and special tests 
of the acids.- 

The members of these five groups will be taken up in the order 
given in the following table. Since the alakli salts of many of the 
acids ionize readily and are soluble , it is advisable to use these in 
the special tests for the acids. 

I. The Volatile Acid Group.—Acids volatilized or decomposed 
when their salts are acted on by dilute nitric, hydrochloric, or sul¬ 
phuric acids. 

H 2 C0 3 , (HCN included in II), HCIO, HN0 2 , H 2 Si0 3 (precipitated), 

H 2 S, h 2 so 3 , h 2 s 2 o 3 . 

II. The Silver Nitrate Group.—Acids whose silver salts are 
insoluble in solutions acidified with dilute nitric acid. 

The following acids are precipitated by AgN (>3 in dilute 
HN0 3 . 

HC1, HBr, HI, HCN, H 4 Fe(CN) 6 , H 3 Fe(CN) 6 , HSCN, HCIO. (See I.) 

The barium salts of this group are soluble in water. 

III. The Barium Chloride Group.—Acids whose barium salts 
are insoluble in water. 

The group is subdivided into two parts: (a) Acids whose 
barium salts are insoluble in dilute acids. The acids precipitated 
by BaCl 2 in dilute acid solutions are: H2SO4, HF, HoSiFe. 

The silver salts of this group are soluble in water. 


156 


QUALITATIVE ANALYSIS 


(6) Acids whose barium salts are soluble in dilute acids. The 
acids precipitated by BaCU in neutral solutions are: 

H 3 PO 4 , H 3 As0 3 , H 3 As0 4 , H 3 B0 3 , H 2 C 1 O 4 , (H 2 C0 3 , H 2 Si0 3 , H 2 S 2 0 3 , H 2 S0 3 , 
H 2 C 2 0 4 , H 2 C 4 H 4 0 6 included in I and V), V 2 0 4 , V 2 0 5 . 

The silver salts of this group are soluble in nitric acid. 

IV. The Soluble Acid Group.—Acids whose barium and silver 
salts are soluble in water. 

The following acids belong to this group: 

HN0 3 (HN0 2 included in Group I), HC10 3 , HMn0 4 (HC 2 H 3 0 2 included 
in Group V). 

V. Organic Acids.—Under this head will be considered: 

(а) Acids which char on heating HC2H3O2, H2C4H4O6. 

(б) Acids which do not char on heating: H2C2O4, H2C7H4O3. 


An additional group may be included of acids that are non¬ 
volatile, which form soluble salts with alkalies alone (Si02, see 
Group I), WO3, Ti02, NU2O5, Ta 205 , Zr0 2 , Zr 203 . 

These acids are not known in the free state, but are found either 
in the anhydride state or combined as salts. The tests of the 
basic elements are given in the latter part of this book. 



THE VOLATILE ACID GROUP 

DESCRIPTIVE 

General Characteristics. 

The acids of this group are volatilized or decomposed when their 
salts are treated with dilute nitric, hydrochloric, or sulphuric acid. 

Individual Characteristics. 

CARBON AND ITS ACID COMBINATIONS 

C, at.wt. 12.0; sp.gr. amorp. 1.75-2.10; cryst.; graphite, 2.25; diamond, 
3.47-3.6585; m.p. sublimes at 3500° C.; oxides, CO and COj. 

The element occurs free in nature in the crystalline forms, diamond and 
graphite, and in the amorphous form, charcoal, coke, etc. It occurs in iron, 
steel, and in certain alloys. 

Combined as a carbonate it occurs in a large number of substances, among 
which are found calcite, marble, limestone, dolomite, magnesite, strontianite, 
witherite, spatic iron ore. It occurs as the dioxide in the air in water 
(H 2 0-C0 2 ) and in flue gas. Carbon dioxide is the active constituent of 
baking powders (NaHC0 3 ). 

Carbonic Acid, H 2 C0 3 , Carbonate—Like sulphurous acid, carbonic 
acid has never been isolated. The anhydride C0 2 mol.wt. 44; sp.gr. 
(A) 1.53; m.p.—65°; b.p.—78.2°. 

Carbon dioxide is a colorless, odorless gas, easily freed from its salts by 
many mineral acids. Since it is but slightly dissociated, it is a feeble acid, 
hence its normal salts are alkaline in reaction. The normal carbonates, 
except those of the alkalies, are insoluble in water; many, however, are 
soluble in excess of C0 2 , forming soluble bicarbonates. All carbonates are 
decomposed by heat except carbonates of the alkalies and BaC0 3 . Nearly all 
carbonate salts are white. 

DETECTION 

Element.—Carbon is recognized by its appearance and by its inertness 
towards general reagents. It is seen in the charring of organic matter when 
heated or when acted upon by hot concentrated sulphuric acid. 

Upon combustion with oxygen or by oxidation with chromic and sulphuric 
acids, carbon dioxide is formed. 


157 




158 


QUALITATIVE ANALYSIS 


Carbon Dioxide.—The gas passed into lime water forms a white precipi¬ 
tate, CaC0 3 . White precipitates are formed when the gas is led into baryta 
water (BaC0 3 ppt.), or into an ammoniacal solution of lead 
acetate (PbC0 3 pptd.). 

Carbonate.—Action of mineral acids causes effervescence, 
C0 2 being evolved. The gas is odorless (distinction from S0 2 , 
H 2 S, and N 2 0 3 ) and is colorless (distinction from N 2 0 3 ). The 
gas absorbed in the reagents above mentioned produces a 
white precipitate. The test is best made by placing the 
powdered material in a large test tube with a stopper carrying 
a funnel and delivery tube as shown in the illustration, Fig. 13. 
For small amounts of combined C0 2 , warming of the test tube 
may be necessary. Sulphuric or phosphoric acid should be 
used to liberate the gas, which is conducted into the reagent 
used for the test. 

Distinction between Soluble Carbonate and Bicarbonate. 

—The solution of the former is alkaline to phenolphthalein 
indicator (pink). Bicarbonate solutions remain colorless with 
this indicator. Normal carbonates precipitate magnesium 
carbonate when added to magnesium sulphate solution; bicarbonates cause 
no precipitation. 

Carbon Monoxide. The gas burns with a violet colored flame and is not 
absorbed by potassium hydroxide or lime water (distinction from C0 2 ). It is 
oxidized to C0 2 and so detected. With hot, concentrated potassium hydrox¬ 
ide potassium formate is produced. 

The gas is detected in the blood by means of the absorption spectrum. 



THE VOLATILE ACIDS OF CHLORINE 
See Silver Nitrate Group for the Element and its other acid combinations. 


Hypochlorous Acid, HCIO, and Hypochlorite 

Among the oxygen acids of chlorine we find: hypochlorous acid, HCIO, 
chlorous acid, HC10 2 , chloric acid, HC10 3 , and perchloric acid, HC10 4 . The 
first of these, hypochlorous acid, is important on account of the use of its 
salts in commerce as bleaching agents. Hypochlorous acid has not been 
isolated. It is a very weak acid and is easily driven from its salts by other 
weak mineral acids. Decomposition takes place at once, chlorine water and 
oxygen being formed. The hypochlorites are consequently strong oxidizing 









THE ACIDS 


159 


agents. When a solution of an alkali hypochlorite is boiled it is converted 
into a chloride and a chlorate. 


DETECTION 

Test for Hypochlorite.—Potassium hypochlorite, KCIO, shaken with 
mercury forms the yellowish red compound Hg 2 OCl 2 , which does not 
form with the other potassium salts of chlorine, i.e., KC1, KC10 2 , KC10 3 , 
KCIO 4 . 

Hypochlorites decolorize indigo, but do not decolorize potassium perman¬ 
ganate solutions. If arsenous acid is present, indigo is not decolorized until 
all of the arsenous acid has been oxidized to the arsenic form. 

Tests for Chlorites.—Potassium permanganate solution is decolorized by 
chlorites. (The solution should be dilute.) 

A solution of indigo is decolorized, even in presence of arsenous acid 
(distinction from hypochlorites), 

NITROUS ACID, HN0 2 , AND NITRITES 1 

HN0 2 occurs as ammonium nitrite to a small extent in the air, in rain 
water, and in mineral springs. It occurs as nitrites in many plant juices 
and in animal mucus. Most of the nitrites dissolve readily in water. The 
silver salt is sparingly soluble. 

DETECTION 

Dilute sulphuric acid or acetic acid added to a nitrite decomposes the salt 
with evolution of nitric oxide, NO, which immediately oxidizes in the air, 

: forming the brown nitrogen peroxide gas, N0 2 . Nitric oxide has a bleaching 
action on potassium permanganate. 

Acetic Acid Test.—Acetic acid added to a nitrite in a test tube (inclined 
as directed in the nitric acid test on pages 201, 203), produces a brown 
ring. Nitrates do not give this. If potassium iodide is present in the solu¬ 
tion, free iodine is liberated. The free iodine is absorbed by chloroform, car¬ 
bon’tetrachloride or disulphide, these reagents being colored pink. Starch 
solution is colored blue. 

Nitrous acid reduces iodic acid to iodine. The iodine is then detected 
| with starch, or by carbon disulphide, or carbon tetrachloride, or chloroform. 

Potassium Permanganate Test—A solution of the reagent acidified with 

1 See nitrogen and its acid combinations, under the Soluble Acid Group, 
j for other acids of nitrogen. 


160 


QUALITATIVE ANALYSIS 


sulphuric acid is decolorized by nitrous acid or nitrite. The test serves to 
detect nitrous acid in nitric acid. Other reducing substances must be absent. 

See tests under Laboratory Exercises, page 165. 

SILICON AND ITS ACID COMBINATIONS 
Si, at.wt. 28.3 ; sp.gr. amor. 2.00; crys. 2.49 ; m.p. 1420° C.; oxides SiO, Si02 

The element silicon has no important application. Its use for electrical 
resistance has been suggested. A rod 10 cm. long with cross-section of 40 
sq.mm, has a resistance of 200 ohms against a carbon rod of the same dimen¬ 
sions of 0.15 ohm. Impure silica finds use in fluxes in manufacture of glass, 
pure silica for the manufacture of silica ware. With caustic it forms an 
adherent sodium silicate. Silicon carbide, carborundum, is used for refractory 
purposes, fire brick, zinc muffles, coke ovens. Crystolon, the crystalline 
form, is used as an abrasive, in making grinding wheels, sharpening stones, etc. 

Combined as Si0 2 and in silicates the element is very widely distributed in 
nature and is a required constituent in practically every complete analysis of 
ores, minerals, soils, etc. It is present in certain alloys, ferro-silicon, silicon 
carbide, etc. 

The element is scarcely attacked by single acids, but is acted upon by 
nitric-hydrofluoric acid mixture. It dissolves in strong alkali solutions. 
Silica is decomposed by hydrofluoric acid and by fusion with the fixed alkali 
carbonates or hydroxides. 

Silicic Acids, Meta, H 2 Si0 3 and Ortho, H 4 Si0 4 . Silicate 

H 2 Si0 3 —mol.wt. 78.32; sp.gr. 1.81. Insol. in cold H 2 0, sol. inalk. 

H 4 Si0 4 —mol.wt. 96.33; sp.gr. 1.57. Slightly sol. in H 2 0, sol. in alk. 

Si0 2 —mol.wt. 60.3; sp.gr. 2.2.-2.6; m.p. 1600-1750°. 

Orthosilicic, metasilicic, and the polysilicic acids all yield Si0 2 on heating. 
The silicates of nature are nearly all derived from the polysilicic acids. 

Silicic acid, H 2 Si0 3 , is one of the weakest of the mineral acids, being 
scarcely ionized at all in solution. The silicates of the alkalies are soluble 
in water. Silicates are transposed by boiling with Na 2 C0 3 . 

General Considerations.—The natural and artifically prepared silicates 
may be grouped under two classes: 1. Those which are decomposed by acids. 
2. Silicates not decomposed by acids. The minerals, datolite, natrolite, 
olivine and many basic slags are representative of the first class, and feldspar, 
orthoclase, pumice and serpentine are representative of silicates not decom¬ 
posed by acids. 


THE ACIDS 


161 


DETECTION 

The finely ground sample together with a small quantity of powdered 
calcium fluoride is placed in a small lead cup 1 cm. in diameter and depth 
| (see Fig. 14) and a few drops of concentrated sulphuric acid added. A lead 
. cover, with a small aperture, is placed on the cup, and 
the opening covered with a piece of moistened black 
filter paper. Upon this paper is placed a moistened 
j pad of ordinary filter paper. The cup is now gently 
heated on the steam bath. At the end of about ten 
minutes, a white deposit will be found on the under 
side of the black paper, at the opening in the cover, if 
an appreciable amount of silica is present in the ma¬ 
terial tested. 

A silicate, fused with sodium carbonate or bicarbonate in a platinum dish 
and the carbonate decomposed by addition of hydrochloric acid with subse¬ 
quent evaporation to dryness, will liberate silicon as silicic anhydride, Si0 2 . 

: The silica placed in a platinum dish is volatilized by addition of hydrofluoric 
': acid, the gaseous silicon fluoride being formed. A drop of water placed in a 
platinum loop, held in the flames of SiF 4 , will become cloudy owing to the 
} formation of gelatinous silicic acid and fluosilicic acid. 

3SiF 4 +3H 2 0 = H 2 SiO 3 +2H 2 SiF 6 . 

If a silicate is fused in a platinum loop with microcosmic salt, the silica 
floats around in the bead, producing an opaque bead with weblike structure 
upon cooling. 

SULPHUR AND ITS VOLATILE ACID COMBINATIONS 

S, at.wt. 32.07; sp.gr. 2.035; m.p. Ill 0 ; b.p. 444.53°; oxides S 2 0 3 , S0 2 , 
SO 3 , S 2 0 7 ; principal acids, H 2 S 2 0 4 , H 2 S0 3 , H 2 S0 4 , H 2 S 2 0 3 , and H 2 S 2 0 8 

Physical properties and chemical reactions are given under Detection. 

The determination of sulphur may be required in a great variety of sub- 
J stances, mineral, rocks, sulphur ores, acids, salts,-water, gas, coal and other 
’ | organic matter. 

The substance occurs in nature principally in the following forms: 

Element.— Found free, generally mixed with earthy matter. The com- 
5 mercial product is exceedingly pure and may contain over 99.5 per cent S. 

Sulphur Dioxide— The gas, together with free sulphur, is found in volcanic 
regions. 

’I Hydrogen Sulphide. —Occurs in mineral waters and in the air, from 
decaying organic matter. 















162 


QUALITATIVE ANALYSIS 


Sulphide Ores.—Iron pyrite, FeS 2 (30 to 50 per cent S); pyrrhotite, 
Fe 7 S 8 ; copper pyrites, CuFeS 2 ; realgar, As 2 S 2 ; orpiment, As 2 S 3 ; galena, 
PbS; cinnabar, HgS; zinc blende, ZnS, are the principal ores. 

Sulphate Ores.—Gypsum, CaS0 4 -2H 2 0, Epsom salts, MgS0 4 -7II 2 0; 
Glauber salt, Na 2 S0 4 -10H 2 O, are the more important sulphates. 

The following facts regarding solubility of sulphur and its combination 
should be kept in mind. 

Element.—The crystalline forms are soluble in CS 2 , the monoclinic form 
is soluble also in alcohol, chloroform and benzol. Yellow amorphous and 
plastic sulphur are insoluble in CS 2 . Sulphur precipitated by the action of 
HC1 upon (NH 4 ) 2 S x is soluble in benzol. The element is soluble in hot 
hydrates of sodium, potassium, barium and calcium, forming polysulphides 
and thiosulphates. 

Sulphide.—Sulphides of Na, K, Cs, Rb, Ca, Sr, Ba, Mg, Mn, Fe are 
soluble in dilute mineral acids. The sulphides of Ag, Hg, Pb, Cu, Bi, Cd, 
Co, Ni require strong acids for decomposition. These are also insoluble in 
sodium hydroxide and potassium hydroxide solutions. As, Sb and Sn sul¬ 
phides are insoluble in dilute acids, but soluble in alkalies. 

Sulphate.—With exception of BaS0 4 , CaS0 4 , SrS0 4 and PbS0 4 , Hg 2 S0 4 ; 
sulphates are soluble in water. 

Thiosulphate.—Nearly all are soluble in water. 

Sulphite.—With exception of the sulphites of the alkalies, sulphites of the 
metals are difficultly soluble in water, but readily decomposed by acids. 

Hydrogen Sulphide, H 2 S, and Sulphide. H 2 S — Mol.wt. 34.09; sp.gr (A) 
1.189; m.p. 85.5°; b.p. 61.8°. Colorless, poisonous gas having the 
disagreeable odor of rotten eggs, burns with blue flame, forming S0 2 +H 2 0. 
Easily displaced by mineral acids, from many of its salts, e.g., sulphides of the 
alkalies, alkaline earths, Mg, Mn, Zn, Fe, less easily from those of Pb, Bi, 
Cd, Sn, Sb, Co, and Ni. Most sulphides are oxidized by cone. HN0 3 or 
Aqua regia, free sulphur being liberated. 

Sulphurous Acid, H 2 S0 3 , and Sulphite.—Among the oxygen acids of 
sulphur, sulphurous acid and thiosulphuric acid are taken up at this point. 
Both are easily volatilized from their salts by dilute mineral acids such as 
HC1, HN0 3 , H 2 S0 4 , the S0 2 gas being liberated. 

Sulphurous acid has never beenisolated. Itis easilyoxidizedtosulphuricacid 
by oxidizing agents such as bromine water,etc. It forms normal and acid salts. 

S0 2 the Anhydride.—Mol.wt. 64.07; sp.gr. (A.) 2.26; m.p —76 1°* 
b.p.—10°. 

Sulphites of the alkalies are deliquescent and are the only sulphites that 
are easily soluble in water. They are readily transposed by boiling with 
water solution of Na 2 C0 3 . 

Thiosulphates are almost all readily soluble in water. 


THE ACIDS 


163 


DETECTION 

The following tests include the detection of free sulphur and its more 
important combined forms. 

Element.—Sulphur is a polymorphous, yellow, brittle, odorless and taste¬ 
less solid; existing in the rhombic, monoclinic and triclinic crystalline forms, 
and also in an amorphous state. At 111 0 it melts to a pale yellow liquid; 
at 180° it thickens to a dark gum-like material, containing a large percentage 
of amorphous sulphur; at 260° it becomes a liquid again, and at 444.53° 
it boils, giving off a brownish-red vapor. 

Heated in the air sulphur burns with a blue flame, and is oxidized to S0 2 , a 
gas with a characteristic pungent odor. This gas passed into a solution of 
potassium permanganate will decolorize it, if S0 2 is in excess of the amount 
that will react with the KMnC >4 in the solution. 

If sulphur is dissolved in a hot alkali solution and a drop of this then placed 
on a silver coin, a stain of black Ag 2 S will be evident, due to the action of the 
sulphur. 

Sulphide.—Hydrogen sulphide, H 2 S, is liberated when a sulphide is 
treated with a mineral acid. This gas blackens moist lead acetate paper. 
H 2 S has a very disagreeable odor, which is characteristic. 

Sulphite.—Sulphur dioxide, S0 2 , is evolved when a sulphite is treated 
with hydrochloric acid. The odor of the gas is characteristic. 

Sulphur dioxide decolorizes a solution of potassium permanganate. (Use 
very dilute solution.) 

Sulphites are distinguished from sulphates by their failure to form a white 
precipitate, when barium chloride is added to the solution acidified with 
hydrochloric acid; also by the fact that H 2 S is formed when zinc is added to a 
solution of a sulphite, acidified by hydrochloric acid. 

Thiosulphate— Sulphur dioxide is evolved and free sulphur precipitated 
when a thiosulphate is acidified with dilute mineral acids. In presence of 
oxidizing agents sulphides will also liberate free sulphur. 

Thiosulphates are strong reducing agents. 

Sulphur Dioxide.— Odor, etc—SO* is evolved when a sulphite is acidified. 
This may be recognized by its odor. It is a strong reducing agent (see above). 
If passed into a solution of KMnCh, it will decolorize it. It is easily oxidized 
to the sulphate form by oxidizing agents such as bromine water. (See separa¬ 
tion of sulphites and sulphates at the close of the tests of this group.) Thio- 
| sulphates liberate S as well as S0 2 ; sulphites liberate only S0 2 . 

Detection of sulphuric acid and sulphates is given under the Barium 
Chloride Group, pages 191, 197. 



164 


QUALITATIVE ANALYSIS 


LABORATORY EXERCISES 

Reactions—Characteristic Tests 
CARBONATE, C0 3 — 

1. Lime Water Test for CO 2 .—CO 2 is liberated with efferves¬ 
cence when a carbonate is acidified with a dilute mineral acid. 

Add a few drops of HC1 to a carbonate solution or salt in solid 
form. A sudden effervescence occurs. Test the gas with a drop 
of Ca(OH) 2 solution on a glass rod or loop tube. A clouding of 
the lime water indicates a carbonate. (CaC 03 formed.) 

Note. —A loop tube is made by bending a capillary glass tube at one end 
into a small loop as in case of platinum wire for borax bead tests. 

Reactions.—CaC0 3 +2HCl=CaCl2 + T CO 2 +H 2 O 
Ca(0H) 2 +C0 2 = i CaCOa+HoO. 

Precaution. —The test will fail if the lime water has been contaminated 
by HC1. An excess of C0 2 will redissolve the insoluble CaC0 3 due to the 
formation of the soluble bicarbonate, Ca(HC0 3 ) , hence the film should be 
examined shortly after exposing it to C0 2 . 

Reactions.—CaCO 3 -fH 2 CO 3 =Ca (HCO 3 ) 2 solution. 

Ca(HC0 3 ) 2 sol. boiled = | CaC0 3 + T C0 2 +H 2 0. 

2. Precipitation from Solution.—BaCb, CaCU, AgN (>3 solu¬ 
tions each precipitate a white compound, BaCC> 3 , CaC 03 or 
Ag 2 C0 3 respectively, when added to neutral solutions of car¬ 
bonates. The precipitates dissolve in acids with evolution of 
CO 2 . Use Na 2 CC >3 solution for the tests. Write out the reactions. 

The student is referred to the descriptive section for detection of carbon 
and its acid combinations for further information on tests. See page 157. 

cyanide; CN- 

1. HCN is liberated by action in an acid on a cyanide. (Hood.) 
The gas is a deadly poison. Tests for cyanides should be made 
according to directions under the Silver Nitrate Group, page 178. 


THE ACIDS 


165 


HYPOCHLORITE, CIO" 

1. Decomposition. —Acidify the solution or solid with dilute 
HC1; the hypochlorite will be decomposed, liberating free chlorine, 
which is recognized by its pungent odor and yellow color. A 
glass rod with a drop of AgN 03 is coated with a white deposit, 
AgCl. Chlorine fumes with NH3, forming NH4CI, a white solid. 

4KC10+4HC1 = 4KC1+ T2Cl 2 +0 2 +2H 2 0. 

2Ca(C10) 2 +2H 2 CO 3 = 2 CaCO 3 + T 2C1 2 +0 2 +2H 2 0. 

Note. —Hypochlorites are strong oxidizing agents. See above reactions. 

In acid or alkaline solution hypochlorites act as free chlorine, a chloride 
being formed and oxidation resulting of substances capable of being oxidized. 

Hypochlorites are distinguished from free chlorine by their 
reaction with mercury, a reddish basic mercuric chloride , Hg 20 Cl 2 , 
being found in place of white, HgCl. 

2. Heat a little KCIO in a small porcelain crucible. The salt 
remaining is KC1, since oxygen gas has been liberated. 

3. (a) Add a little of the salt to a solution of indigo. Note 
that the color is destroyed. 

( 1 b ) Try the test with a weak solution of KMnC>4. Note 
that the color remains. 

Note. —Note distinction of chlorites from hypochlorites in the descriptive 
section, pages 158, 159. 

NITRITE, N0 2 - 

1. Potassium Iodide Test with (a) Starch— Acidify a solution 
of KI and starch with dilute H 2 S0 4 and add a few drops to a 
solution containing a nitrite. The reagent should be in sufficient 
amount to make the solution acid. A blue color results. (The 
oxidizing nitrite liberates free iodine, which in turn forms a blue 
compound with starch.) 

(b) Carbon Disulphide. —In place of the starch in the above 
test use CS 2 and shake. CS 2 colored violet settles to the bottom 
of the solution. (CS 2 +I.) 





166 


QUALITATIVE ANALYSIS 


2. Decomposition with Acids. —(a) Dilute H 2 SO 4 decomposes 
nitrites with liberation of nitric oxide. In presence of air NO 
oxidizes to brown NO 2 . Nitrates are not decomposed by dilute 
H 2 SO 4 . See test for nitrates in the Soluble Acid Group, page 201. 

Reactions.—3NaN0 2 +3H 2 S0 4 = HN 0 3 + 3 NaHS 04 + T 2N0+H 2 0, 
and N0+0 = N0j brown gas. 

(b) Nitrites are decomposed by warming with acetic acid; 
nitrates are not decomposed. 

3. Potassium Permanganate. —To an acid solution of KMn 04 
add NaN02. The color is destroyed. Compare this test with 
that of KCIO, Test 3 under Hypochlorite, on page* 165. 

2 KMn 04 + 5 NaN 0 2 + 3 H 2 S 04 =K 2 S 04 + 2 MnS 0 4 + 5 NaN 03 + 3 H 2 0 . 

4. Cobalt Salts. —Acetic acid solutions of cobalt salt produces 
a yellow precipitate, K3Co(N02)6. Make the test with a fairly 
strong solution of KNO 2 . 

Note. —See test for Cobalt under Ammonium Sulphide Group, pages 
85, 103. 

5. Silver Nitrate precipitates white AgN (>2 from cold solutions. 

KNOo+AgNOa = i AgN0 2 +KN0 3 . 

6. Test in Water Analysis. —Acidify a dilute solution with a 
drop or so of HC1, add 2 cc. of sulphanilic acid solution and 2 cc. 
of naphthalamine hydrochloride. Nitrites cause a pink colora¬ 
tion. This test is used in a quantitative determination in water 
analysis. 

SILICATE, Si0 3 - 

1. Microcosmic Salt Test— Fuse a little of the silicate salt 
with microcosmic salt in a platinum loop; the silica floats around 
in the bead, producing on cooling an opaque bead with weblike 
structure. 

2. Make a test with hydrofluouric acid according to directions 
given under detection of Silicon in the descriptive section, page 161. 



THE ACIDS 


167 


3. Insoluble Silicate. —Fuse with Na 2 C 03 +K 2 CC >3 until effer¬ 
vescence ceases. Add HC1 to acid reaction. Silicic acid is formed. 
Evaporate to dryness, add HC1, and dilute with water. The 
bases will dissolve, but silica is left as a gelatinous, insoluble 
substance. The precipitate Si (>2 warmed with CaF 2 and strong 
H 2 SO 4 in a lead tube, liberates gaseous SiF 4 . If the gas is con¬ 
ducted into water gelatinous silicic acid is formed. 

3SiF 4 +3H 2 0 = 1 H 2 Si0 3 +2H 2 SiF 6 . 

SULPHIDE, S— 

1 . Lead Acetate. —Add a few drops of dilute (1:1) HC1 
to the solid in a test tube and warm gently. Hold a filter paper 
moistened with Pb ( 02 ^ 02)2 solution over the mouth of the tube. 
A black discoloration is due to H 2 S. (PbS, black, formed.) 
Note the characteristic odor of H 2 S. 

(a) FeS+2HCl = TH 2 S+FeCl 2 . 

(6) H 2 S+Pb(C 2 H 3 0 2 ) 2 = | PbS+2HC 2 H 3 0 2 . 

2. Oxidizing Agents. —Add concentrated nitric acid or HC1 
+KCIO 3 to a sulphide. Note liberation of sulphur. 

2HN0 3 +3H 2 S = 1 3S+ 12N0+4H 2 0. 

Further oxidation occurs on heating as follows: 

4S+8HN0 3 = 4H 2 S0 4 + T8NO. 

3. Silver Coin Tests for Insoluble Sulphide.— In case the 
; above test is negative and a colored residue remains, wash and 
1 dry, fuse in a porcelain crucible with a piece of NaOH, dissolve the 
solid Na 2 S in a little water and place a drop on a silver coin. A 
sulphide will leave a black stain (Ag 2 S). Write out reaction. 

4. Flame. —H 2 S burns with blue flame. 

2H 2 S+30 2 = T2S0 2 +2H 2 0. 



168 QUALITATIVE ANALYSIS 

SULPHITE, S0 3 — 

1. Ferric Chloride Ferrocyanide Test.—Acidify the sulphite salt 
with dilute HC1 (using a test tube). Place a drop of a mixture 
of FeCl 3 and K 3 Fe(CN) 6 in a loop tube and expose to the fumes 
arising from the sulphite. The drop is colored blue [Fe 3 [Fe(CN) 6 ] 2 , 
Turnbull's blue). Ferric chloride is reduced to ferrous state 
which reacts with K3Fe(CN)6. 

2. Sulphur Dioxide (a) Odor. —SO 2 is evolved when a sulphite 
is acidified. This can be recognized by its odor. 

Na 2 S0 3 +2HCl = ! S0 2 +2NaCl+H 2 0. 

(6) SO 2 is a strong reducing agent (see above). If passed 
into a solution of KMnCU, it will decolorize the reagent. 

2 KMnO 4 +5S0 2 +2H 2 0 = 2MnSO 4+ K 2 SO 4 + 2 H 2 SO 4. 

(c) It is easily oxidized to the sulphate form by oxidizing agents 
such as bromine water or solution of iodine; the color is bleached. 

Br 2 +SO 2 +H 2 0 = H 2 SO 4 +2HBr. 

( 1 d ) Sulphur dioxide conducted into an acid solution of K 2 Cr 207 
produces a green color due to reduction of chromic salt. (See 
chromium, page 94.) 

K 2 Cr 2 07 3SO 2 -f* H 2 SO 4 = Cr 2 (SO 4) 3 +K 2 SO 4 F H 2 0. 

(See separation of sulphites and sulphates at the close of the tests 
of this group.) Thiosulphates liberate S as well as SO 2 ; sulphites 
liberate only SO 2 . 

THIOSULPHATE, S 2 0 3 — 

1. Acidify a little of the salt in a test tube with a few drops of 
HC1; SO 2 will be evolved (note the color) and free sulphur 
deposited. 

2Na 2 S 2 0 3 +4HCl = t S 0 2 + [ S 2 +4NaCl+2H 2 0. 

Note .—With oxidizing agents present H 2 S also liberates free sulphur. 







THE ACIDS 


168a 


Silver nitrate solution gives a white precipitate, turning to 
yellow, brown and finally black. 

Na 2 S 2 0 3 +2AgN0 3 =2NaN0 3 +Ag 2 S 2 0 3 

and 

Ag 2 S 2 0 3 +H 2 0 = Ag 2 S+H 2 S0 4 . 

Silver thiosulphate is soluble in excess of thiosulphate. On 
boiling SO 2 is evolved, Ag 2 S (black) precipitated with free S. 

Reaction. 

(а) Ag 2 S 2 0 3 +Na 2 S 2 0 3 =2Na(AgS 2 0 3 ). 

(б) 2Na(AgS 2 0 3 )+Na 2 S 2 0 3 = Na 4 (Ag 2 (S0 3 ) 3 ) sol. 

(c) Boiling forms Na 2 S0 4 +S0 2 -fS+Ag 2 S. 

Barium chloride produces a white crystalline precipitate dif¬ 
ficultly soluble in cold water but fairly soluble in hot. 

Strontium chloride gives a white crystalline precipitate from a 
concentrated solution. (N. B. solubility on page 289.) 

Lead acetate gives a white precipitate, soluble in an excess of 
the alkali thiosulphate. On boiling the solution thus obtained 
lead sulphate and sulphide precipitate. 

Zinc salts produce no precipitate. Distinction from sulphide. 


Distinction between Acid and Normal Sulphites, NaHSOs 
and Na 2 S 03 

The acid sulphite (bisulphite) is neutral to methyl orange 
indicator and acid to phenolphthalein. The normal sulphite is 
alkaline to methyl orange and neutral to phenolphthalein. Advan¬ 
tage is taken of these facts in the quantitative determination of 
the two acids, when present in the same solution. 

To a portion of the sample dissolved in water is added methyl 
orange, if the solution is yellow the normal sulphite is indicated, 





1686 


QUALITATIVE ANALYSIS 


should a drop of dilute acid cause a red color the normal salt is 
absent, or present in very small amount. If the solution is 
immediately colored red only the acid sulphite is present. 

To a second portion add phenolphthalein. If the solution is 
colorless the acid salt is indicated. A drop of dilute alkali chang¬ 
ing the solution to violet red or pink indicates the absence of the 
acid salt. . If the solution is immediately colored on addition of 
the indicator the absence of the acid salt is confirmed. The acid 
and alkali reagents should be very dilute for delicate tests. (N/10 
solutions.) 

Reactions. Neutral sulphite: 

Na 2 S0 3 (M. O. yellow)+HCl = NaHS0 3 (M.O. orange red)+NaCl. 

Acid sulphite: 

NaHS0 3 (P. colorless) +Na0H = Na 2 S0 3 (P. violet red)+H 2 0. 

(See Scott, “ Standard Methods of Chemical Analysis ” for 
quantitative determination.) 


Separation and Detection of Sulphide, Thiosulphate, and Sulphite 
in Presence of One Another 

The strong solution of the alkali salts is treated with zinc sulphate. 


Precipitate.—ZnS. 
Confirm. 


Filtrate.—Sulphite and thiosulphate. 

Add strontium nitrate and settle for several hours. 
Filter and wash the precipitate. 


Precipitate.—SrS0 3 . 

Add dilute HC1. S0 2 is given 
off. Iodine sol. decolorized. 


Solution thiosulphate. 

Add HC1 and warm. Free sulphur 
clouds the solution. 








THE ACIDS 


169 


Separation and Detection of Sulphate and Sulphite 
j Acidify the cold solution and add BaCl 2 in excess. Filter. 

Precipitate.—BaS0 4 , white, Filtrate contains the sulphite. Add Br 
j proves presence of H 2 SO 4 . water: a white ppt. of BaS0 4 proves the 

presence of a sulphite. (Sulphite oxidized to 
sulphate, thiosulphates being absent.) 


Analysis of Volatile Acid Group—Summary 


To a small amount of the solid unknown add dilute sulphuric acid. An 
effervescence will occur due to the liberation of gases. 


Reaction 


Inference 


Odor of rotten eggs, blackens lead acetate paper. 
Brown fumes, decolorizes KMn0 4 , iodine, etc. 
Liberates S0 2 and free sulphur. 

Liberates S0 2 , odor of the gas distinctive—burning S. 
Rapid effervescence, lime water made turbid. 
Chlorine evolved, noted by color and odor. 

Slight flocculent precipitate on adding water. 

HCN may be evolved—odor of bitter almonds (poison). 
Heating may cause acetic acid to evolve, also HCN, 
CO, O, etc. 


H 2 S, sulphide. 

HN0 2 , nitrite. 
H 2 S 2 0 3 , thiosulphate. 
H 2 S0 3 , sulphite. 
H 2 C0 3 , carbonate. 
HCIO, hypochlorite. 
H 2 Si0 3 , silicate. 


Exercises—The Volatile Acid Group 


1 . If a sulphide and sulphite are both present in a sample, what product is 
formed when the material is acidified? 

2. How would you distinguish between a carbonate and a sulphite if 
both are present in solution? 

3. If a green color results when the gases evolved from an unknown, 
acidified with sulphuric acid, are passed into a solution of potassium dichro¬ 
mate, what gases are apt to be present? 

4. If, on testing for sulphides with lead acetate paper, a yellow color 
results, what is present in the substance? 

5 . How can you distinguish between a sulphite and sulphate? 

6 . How can you distinguish between a nitrite and nitrate? 

7. How would you test for oxygen if a perchlorate were present in the 
substance being analyzed? 

8 . State other methods for making confirmatory tests for H 2 S, S0 2 , Cl 2 , 
and C0 2 than the ones given under the exercises. Study Table of Reactions 
in Part V, 














SILVER NITRATE GROUP 

DESCRIPTIVE 


General Characteristics. 

Members of this group are precipitated by Silver Nitrate from 
solutions containing dilute nitric acid. These acids are not 
precipitated by Barium chloride. 

Individual Characteristics. 

CHLORINE AND ITS ACID COMBINATIONS 

Cl 2, at.wt. 35.46; D. (air), 2.491; m.p. —101.5°; b.p. —33.6° C.; oxides, 

CI2O, CIO21 CI2O7. 

Hydrochloric Acid—HC1.—Mol. wt. 36.47; sp.gr. (air) 1.27; m.p. —112.5°; 
b.p. —83.1°. Solubility in 100 cc. H 2 0 at 10° is 82.5 g. Concentrated solu¬ 
tion of HC1 contains 40 per cent of the gas by weight (sp.gr. 1.20). At boiling 
point 20 per cent. 

Cl 2 -—At.wt. 35.46; sp.gr. (A) 2.49; m.p. -102°; b.p. 33.66°. Color, 
greenish yellow. Liberates Br and I from their salts. Causes starch iodide 
paper to turn blue, due to liberation of iodine. Decolorizes litmus. 

Chlorine occurs only in combination. It is found in all plants and animals; 
occurs in horn silver, AgCl; phosgenite, PbCl 2 ; in large quantities in carnel- 
lite, MgCl2+KCl+6H 2 0; sylvine, KC1; rock salt, NaCl; also combined 
with K, Na, Mg in sea water and salt springs. 

Salts. —Most chlorides are deliquescent except those of Ag, Hg, Pb, Cd, 
Co, Ba, Sr, K, Na, NH 4 . All soluble chlorides are readily transposed into 
carbonates by boiling with sodium carbonate, the insoluble salts by fusion 
with the dry Na 2 C0 3 . AgCl is not decomposed when heated to dull redness, 
but is decomposed by sulphuric acid and zinc, forming HC1, ZnS0 4 , and Ag. 

Although chlorides are nearly all soluble in water, silver chloride is practi¬ 
cally insoluble (100 cc. dissolves 0.000152 gram at 20° C.); mercurous chloride 
is nearly as insoluble as silver chloride (0.00031 gram); lead chloride requires 
heat to bring it into solution (in cold water only 0.673 gram soluble per 100 cc. 
of water). Chlorides of antimony, tin, and bismuth require free acid to keep 
them in solution. A large excess of HC1 increases the solubility of silver, mer- 

170 


THE ACIDS 


171 


cury, lead, antimony, bismuth, copper (Cu~), gold and platinum, but decreases 
the solubility of cadmium, copper (Cu ),nickel, cobalt, manganese, barium, 
calcium, strontium, magnesium, thorium, sodium, potassium and ammonium 
I chlorides. 

Chlorine gas is most readily dissolved in water at 10° C. (1 vol. H 2 0 dis- 
j solves 3.095 vols. Cl). Boiling completely removes chlorine from water, 
i Hypochlorites, chlorites, chlorates, and perchlorates are soluble in water. 

The chlorine may be present either combined or free. In the combined 
state it may be present as free hydrochloric acid or as a water-soluble or insol¬ 
uble salt. 

DETECTION 

Free Chlorine.—The yellow gas is recognized by its characteristic odor. 
It liberates iodine from iodides; it bleaches litmus, indigo, and many organic 
i coloring substances. 

Chlorides. Silver Nitrate Test—In absence of bromides and iodides, 

! which also form insoluble silver salts, silver nitrate precipitates from solutions 
I containing chlorides white, curdy, silver chloride, AgCl (opalescent with 
traces), soluble in NH 4 OH (AgBr slowly soluble, Agl difficultly soluble), also 
soluble in concentrated ammonium carbonate (AgBr is very slightly soluble; 
Agl is insoluble). Silver chloride turns dark upon exposure to light. 

Detection in Presence of Cyanate, Cyanide, Thiocyanate. An excess of 
silver nitrate is added to the solution, the precipitate filtered off and boiled 
j with concentrated nitric acid to oxidize the cyanogen compounds and the 
; white precipitate, silver chloride, subjected to the tests under chlorides to 
I confirm the compound. 

Detection in Presence of Bromides and Iodides.—See Exercises, page 182. 

If Chlorates are Present.—The halogens are precipitated with silver 
nitrate, the precipitate dissolved with zinc and sulphuric acid and the solution 
treated as directed on page 182. 

Test for Hypochlorite.—Potassium hypochlorite, KCIO, shaken with mer¬ 
cury, forms the yellowish-red compound Hg 2 OCl 2 , which does not form with 
the other potassium salts of chlorine, i.e., KC1, KC10 2 , KCIO?, KC10 4 . 

Hypochlorites decolorize indigo, but do not decolorize potassium perman- 
ganate solutions. If arsenous acid is present, indigo is not decolorized until 
all of the arsenous acid has been oxidized to the arsenic form. .... 

Tests for Chlorite.—Potassium permanganate solution is decolorized by 

, chlorites. (The solution should be dilute.) 

A solution of indigo is decolorized, even in presence of arsemous acid 

! (distinction from hypochlorites). . 

Detection of Chlorate— The dry salt heated with concentrated sulphuric 

j acid detonates and evolves yellow fumes. 




172 


QUALITATIVE ANALYSIS 


Chlorates liberate chlorine from hydrochloric acid. 

Perchlorate.—The solution is boiled with hydrochloric acid to decompose 
hypochlorites, chlorites and chlorates. Chlorides are removed by precipi¬ 
tation with silver nitrate, the filtrate evaporated to dryness, the residue fused 
with sodium carbonate to decompose the perchlorate to form the chloride, 
which may now be tested as usual. 


BROMINE 

Br, at.wt. 79.92; sp.gr. 3.1883°; m.p. —7.3°; b.p. 58.7° C.; acids, HBr 

HBrO, HBr0 3 . 

Hydrobromic Acid—HBr. —Mol.wt. 80.93; sp.gr. (air) 2.7+, m.p. —86.13°; 
b.p. —68.7°. . Solubility in 100 cc. H 2 0 at 0° is 221.2 g. Br 2 .—At.wt. 79.92; 
sp.gr. 3.188; m.p. —7.3°; b.p. 58.7°. 100 cc. of water at 0° dissolves 4.17 g. 

Hot water 3.5 gms. Soluble in CS 2 , ether, alkalies, alcohol, chloroform. 

The element is a dark, brownish-red, volatile liquid, giving off a dark 
reddish vapor with suffocating odor, irritating the mucous membrane (anti¬ 
dote dilute NH 4 OH, ether), very corrosive. Acts violently on hydrogen, 
sulphur, phosphorus, arsenic, antimony, tin, the heavy metals, and on potas¬ 
sium, but has no action on sodium, even at 200° C. Bleaches indigo, litmus, 
and most organic coloring matter. It is a strong oxidizing agent. Bromine 
displaces iodine from its salts, but is displaced by chlorine from its com¬ 
binations. 

Bromine never occurs free in nature. It is found chiefly combined with 
the alkalies and the alkaline earths, hence occurs in many saline springs and 
is a by-product of the salt industry. It is found in Silician zinc ores, Chili 
saltpeter, in sea water (probably as MgBr 2 ), in marine plants. Traces occur 
in coal, hence in gas liquors. 

The following facts regarding solubility should be remembered. The 
element bromine is very soluble in alcohol, ether, chloroform, carbon disulphide, 
carbon tetrachloride, concentrated hydrochloric acid and in potassium bromide 
solution. One hundred cc. of water at 0° C. is saturated with 4.17 grams of 
bromine, and at 50° C. with 3.49 grams. The presence of a number of salts 
increases its solubility in water, e.g., BaCl 2 , SrCl 2 , etc. 

Bromides are soluble in water, with the exception of silver, mercury, lead, 
and cuprous bromides. 

Bromates are soluble in water with the exception of barium and silver 
bromates and some basic bromates. 

The soluble bromides are readily transposed by boiling with Na 2 C0 3 ; 
the insoluble salts by fusion with dry Na 2 C0 3 . AgBr is not decomposed 


THE ACIDS 


173 


when heated to a dull redness, but when acted upon by Zn and H 2 SO 4 , forms 
HBr+ZnS0 4 +Ag. 

DETECTION 

Silver Nitrate solution precipitates silver bromide, AgBr, light yellow, 
from solutions containing the bromine anion. The precipitate is insoluble 
in dilute nitric acid, but dissolves with difficulty in ammonium hydroxide 
and is practically insoluble in ammonium carbonate solution (distinction from 

; Agci). 

Carbon Disulphide or Carbon Tetrachloride or Chloroform shaken with 
! free bromine solution, or with a bromide to which a little chlorine water has 
| been added (a large excess of chlorine must be avoided, as this forms BrCl 
compound), will absorb the bromine and become a reddish-yellow color, or 
if much bromine is present, a brown to brownish-black. In the latter case a 
smaller sample should be taken to distinguish it from iodine. 

Bromates are first reduced by a suitable reducing agent such as cold oxalic 
I acid, sodium nitrite, hydrochloric acid, etc., and the liberated bromine tested 
i as directed above. Silver nitrate added to bromates in solution precipitates 
AgBr0 3 , which is decomposed to bromine gas by hydrochloric acid. 

IODINE 

I, at.wt. 126.92; sp.gr. 4.948 17 °; m.p. 113.6°; b.p. 184.4° C.; acids, HI, 

HIO, HIO s , HI0 4 . 

t The element is found free in some mineral waters; combined as iodides 
j and iodates in sea water; in ashes of sea plants; small quantities in a number 
' of minerals, especially in Chili saltpeter as sodium iodate, hence in the mother 
liquor from the Chilian niter works from which iodine is principally produced, 
i Sea-weed ash (drift kelp, Laminaria digitata and L. stenophylla) is an impor¬ 
tant source of iodine. 

Hydriodic Acid—HI. —Mol.wt. 127.93; sp.gr. (air) 4.37; m.p.—51.3°; 
i b.p. — 34 . 1 °. Very soluble in water and in alcohol. 

I 2 .—At.wt. 126.92; sp.gr. 4.95; m.p. 114.2°; b.p. 184.35°. 

Very slightly soluble in water. Soluble in KI, CS 2 , alcohol, chloroform, 
| ether. Gray black, rhombic solid. Occurs combined with K, Na, Ca, Mg, 
in certain salt springs and also in sea water. It is found in Chili saltpeter, 
in certain rock salts, in many plants, in muscle tissue, blood, milk, eggs, and 
in fresh water animals. It occurs rarely as Agl, Pbl in certain minerals. 

Iodides are easily soluble in water, with the exception of Agl, Hgl, Hgl 2 
: and Pbl 2 . All soluble iodides are transposed by boiling with Na 2 C0 3 , the 



174 


QUALITATIVE ANALYSIS 


insoluble iodides by fusion with the dry carbonate. Agl is not decomposed 
when heated to dull redness. It is acted on by Zn and H 2 SO 4 , forming 
HI+ZnS0 4 +Ag, but the heat during a vigorous reaction will liberate free 
iodine. The element is liberated from its salts by Br and Cl; also by H 2 SO 4 , 
concentrated, and by certain oxidizing agents. 

DETECTION 

The element may be recognized by its physical properties. It is a grayish 
black, crystalline solid, with metallic lustre, brownish-red in thin layers. It 
vaporizes at ordinary temperatures with characteristic odor. Upon gently 
heating the element the vapor is evident, appearing a deep blue when unmixed 
with other gases, and violet when mixed with air. It colors the skin brown. 
Chemically it behaves very similarly to chlorine and bromine. 

Free iodine colors water yellow to black, carbon disulphide violet, ether 
or chloroform a reddish color, cold starch solution blue. 

Tannin interferes with the usual tests for iodine, unless ferric chloride is 
present. 

Iodide.—The dry powder, heated with concentrated sulphuric acid, evolves 
violet fumes of iodine. Iodine is liberated from iodides by solutions of As 5 , 
Sb 5 ,Bi 5 , Cu 2 , Fe 3 , Cr 6 , H 3 Fe(CN) 6 , HN0 2 , Cl, Br, H 2 0 2 , ozone. 

Insoluble iodides may be transposed by treatment with H 2 S, the filtered 
solution being tested for the halogen. 

Iodate.—The acidulated solution is reduced by cold solution of S0 2 , or 
K 4 Fe(CN) 6 , (acidulated with dilute H 2 S0 4 ), or by Cu 2 Cl 2 , H 3 As0 3 , FeS0 4 , 
etc. An iodate in nitric acid may be detected by diluting the acid with water, i 
adding starch solution, then hydrogen sulphide water, drop by drop, a blue 
zone forming in presence of the substance. 

HYDROCYANIC ACID, HCN 

Mol. wt. 27.02; sp.gr. 0.697; m.p. —15°; b.p. 26.1°. Very soluble in 
water, alcohol, ether, etc. 

C 2 N 2 .—Mol. wt. 52.02; sp.gr. 1.806 (A); m.p. —39°; b.p. —22°. 

Hydrocyanic acid exists in the seeds of certain plants. 

Commercial salts of cyanogen—KCN; K 4 Fe(CN)e, yellow prussiate of 
potash; K 3 Fe(CN) 6 , red prussiate of potash. 

Prussic acid, HCN, and most cyanides are poisonous, and great care 
should be used in handling them. The cyanides of the alkaline earths and 
the alkalies and Hg(CN )2 are soluble in water; most of the other cyanides are 
insoluble. All cyanides are transposed by boiling with Na 2 C0 3 . AgCN 
is insoluble in dilute HN0 3 , but soluble in KCN, NH 4 OH, or (NH 4 ) 2 C0 3 . 






THE ACIDS 


175 


It is decomposed when heated to dull redness, Ag 2 +C 2 N 2 being formed. 
HCN is a weak acid and is liberated from its alkaline salts by organic acids. 

Detection. —See Laboratory Exercises, page 178. 

HYDROFERROCYANIC ACID, H 4 Fe+ + (CN) 6 

A white crystalline powder soluble in water. Its principal salts, potassium 
ferrocyanide, ferriferrocyanide, Prussian blue, Fe 4 [Fe(CN) 6 ]3. Ferrocyanides 
of alkalies and alkaline earths are soluble in water; most other ferrocyanides 
are insoluble in water and cold acids. They are transposed by boiling with 
(NaiCOs or NaOH and are easily oxidized to ferricyanides by oxidizing agents. 
K 4 Fe(CN)«, boiled with concentrated H 2 S0 4 , is decomposed. HCN is 
liberated if the acid is dilute. Ag 4 Fe(CN) 6 , heated to dull red, is decom¬ 
posed, metallic silver being deposited. 

Detection. See Laboratory Exercises, page 179. 

HYDROFERRICYANIC ACID, H 3 Fe + + + (CN) 6 

Brownish crystals. Its principal salts are potassium ferricyanide, and 
ferroferricyanide, Turnbull’s blue, Fe 3 [Fe(CN) 6 ] 2 . With exception of the 
alkalies and alkaline earths all ferricyanides are insoluble in water and in 
cold dilute acids. Dilute warm H 2 S0 4 causes a partical decomposition, 
HCN being- liberated. Strong hot H 2 S0 4 liberates CO. Ferricyanides 
decompose, when highly heated, nitrogen and cyanogen gas being liberated 
and iron carbide and cyanide being formed. The ferricyanide may be reduced 
i to the ferrocyanide. 

Detection. See tests under Laboratory Exercises, page 180. 

THIOCYANIC OR SULPHOCYANIC ACID, HCNS 

Mol. wt. 59.11; m.p. —12.5°. Very soluble in water. Colorless, irritating 
i liquid. Colors ferric salts red, forming Fe(CNS) 3 . Other salts, KCNS, 
; NaCNS, NH 4 CNS, Hg(CNS) 2 . The thiocyanates, with the exception of 
those of Ag, Hg, Pb, Cu, are soluble in water. AgCNS dissolves in an excess 
of NH 4 OH. 

Detection tests given under Laboratory Exercises, page 180. 



176 


QUALITATIVE ANALYSIS 


LABORATORY EXERCISES 

Reactions—Characteristic Tests 

Use the potassium or sodium salts of the acids. 

CHLORIDE, Cl“ 

1. (a) Silver Nitrate precipitates AgCl, white, curdy pre¬ 
cipitate from a solution containing a chloride. 

(6) AgCl dissolves in strong HC1. 

(c) The salt is insoluble in dilute HNO 3 . 

( 1 d ) The precipitate exposed to the light turns to a lavender 
and finally to a black color. 

(e) It is soluble in NH4OH, forming the readily ionized salt 
Ag(NH 3 )2 + Cl- 

(/) It is reprecipitated upon acidifying the solution ( e ) with 

HN0 3 . 

( 1 g ) AgCl is soluble in (NIL^COs and KCN. 

Prove each of the statements by laboratory tests. Write out 
reactions. 

Note. —If chlorine is combined with silver decomposition may be accom¬ 
plished by adding metallic zinc and sulphuric acid and allowing the reaction 
to continue until the chloride is transposed. The solution is now filtered 
from metallic silver and may be tested for chloride. 

2AgCl+Zn(+zH 2 S0 4 ) = j 2Ag+ZnCl 2 + (zH 2 S0 4 ). 

2. Dichromate Test.—(a) Make a mixture of the dry chloride 
salt and K 2 Cr 207 , add concentrated H 2 SO 4 and heat. The red¬ 
dish brown gas is chromyl chloride. If the gas is now absorbed 
in NH4OH, ammonium chromate will form with its characteristic 
yellow color. Bromides and iodides do not interfere if present in 
moderate amount. 

Reactions.—( a ) 4NaCl4-K 2 Cr 2 07-}-6H 2 S0 4 = t Cr0 2 Cl 2 -l-4NaHS0 4 
+2KHS0 4 +3H 2 0. 

(6) 4NH 4 0H+Cr0 2 Cl 2 =(NH 4 ) 2 Cr0 4 +2NH 4 Cl+2H 2 0. 








THE ACIDS 


177 


Note .—Bromine and iodine are liberated by the action of K 2 Cr 2 0 7 and 
H 2 S0 4 . They combine with NH 4 OH, forming colorless ammonium salts. 

Study the section on detection of chlorine on page 171. 

BROMIDE, Br~ 

1 . (a) Silver Nitrate precipitates AgBr from solutions con¬ 
taining the Br“ anion. 

( b ) AgBr is insoluble in dilute HNO 3 . 

(c) The light yellow precipitate darkens in the light. 

(d) It dissolves with difficulty in NH 4 OH and is insoluble in 
cold (NH 4 ) 2 C 03 . Prove statements by tests with a soluble base. 

2. Chlorine Test.—A water solution of the free halogen added 
drop by drop to a solution of a bromide salt liberates bromine. 
The free bromine may be recognized by adding carbon disulphide 
or chloroform and shaking the mixture, bromine colors the 
reagent yellow or reddish yellow. An excess of chlorine should be 
avoided, as the colorless BrCl would form. 

Reaction.—KBr+Cl = t Br+KCl. 

| 3. Potassium nitrate added to a bromide solution containing 

dilute H2SO4 does not liberate bromine. Note distinction from 
iodide. 

IODIDE, I- 

1 . (a) Silver Nitrate precipitates Agl from a solution of an 
iodide acidified with HNO3. 

(6) The yellow precipitate is insoluble in cold NH4OH and 
| in (NH4) 2 CO 3 . Make tests and write reaction. 

2. Chlorine Test . 1 — Carbon Disulphide, shaken with an iodine 
compound to which chlorine water has been added, is colored 
violet by the liberated iodine. CS 2 , being heavier than the solu- 

1 Iodine is also liberated from solutions of iodides by concentrated 
, H 2 SO 4 , H 2 S0 4 +Mn0 2 , Na 3 As0 3 +HN0 3 , ferric salts in acid solution, cupric 
salts (2CuS0 4 H-4KI = i 2 CuI (yellowish brown) + i 2I+2K 2 S0 4 ). 





178 QUALITATIVE ANALYSIS 

tion, settles to the bottom of the containing vessel. As in case of 
bromides an excess of chlorine should be avoided, since the colorless 
iodic acid would form. Prove this. 

Reactions.—KI+C1 = I+KC1. 

1 2 -f 5 CI 2+6 H 2 0=2HIO 3 +10HC1. 

3. Nitrite Test. —Potassium nitrite added to a solution of 
an iodide, acidified with H2SO4, liberates iodine. This may be 
recognized by the yellow color imparted to the solution or by 
absorbing in CS 2 , or CHCI3, a violet color becoming evident. 
The liberated iodine colors a dilute solution of starch blue. Note 
distinction from bromides. 

4. Potassium Dichromate sets iodine free from water solutions 
as iodides. A few drops of dilute starch solution will cause a 
blue coloration due to the action of free iodine on starch. 

Reaction.— 6 KI+K 2 Cr 2 07 + 7 H 2 S 04 = 1 3I 2 4-Cr 2 (S0 4 ) 3 +4K 2 S0 4 +7H 2 0. 

5. Mercuric Chloride Test.— HgCl 2 precipitates scarlet Hgl 2 
from solutions of iodides. The compound is soluble in an excess 
of alkali iodide. 

(а) 2KI+HgCl 2 = 1 Hgl 2 (scarlet)+2KC1. 

(б) Hgl 2 -f 2KI = K 2 HgI 4 . 

CYANIDE, CN~ 

1. Silver Nitrate, added in excess to a cyanide, produces 2 
white, flocculent precipitate, AgCN, soluble in KCN and ir ■ 
NH4OH, but is reprecipitated from these solutions by HNO3 
Use a solution of KCN. 

Reactions.— (a) KCN+AgNCh = l AgCN+KNCb. 

(6) AgCN -fKCN = KAg(CN) 2 . 







THE ACIDS 


179 


2. Ammonium Polysulphide Test. Formation of Thiocyanate. 
—If few drops of (NH^Sx is added to a solution containing a 
cyanide, the mixture evaporated to dryness, then dissolved in 
HC1, and a few drops of FeCl 3 added, a red color, due to the 
formation of Fe(SCN) 3 , is obtained. The test may be carried 
out thus. Add to the cyanide a little dilute H 2 SO 4 in a test tube, 
distill a few drops into a test tube containing about 1 cc. (NH^Sx. 
Evaporate to dryness in a small porcelain dish, cool, and add a 
drop of FeCl 3 . A red coloration will result due to ferric thio¬ 
cyanate formed. 

3. Formation of Prussian Blue.—The alkali cyanide is made 
strongly alkaline with NaOH and a little FeS04 and FeCU added, 
the mixture gently heated, then made acid with HC1 (Hood) 1 a 
precipitate of Prussian blue, Fe4(Fe(CN)e)3> is obtained. 

Reactions. —FeSC> 4 + 2 NaOH = [ Fe( 0 H) 2 +Na 2 S 04 . 

Fe(OH) 2 + 6 KCN=K 4 Fe(CN) 6 +2KOH. 

3 K 4 Fe (CN) 6 +4FeCl 3 = Fe 4 [Fe (CN) 6 ] 3 +12KC1. 


FERROCYANIDE, (Fe+ + (CN) 6 )- 

1. Silver Nitrate precipitates Ag 4 Fe(CN) 6 , white, insoluble 
in NH 4 OH. 

K 4 Fe(CN) 6 +4AgNO 3 - i Ag 4 Fe(CN)8+4KN0 3 

2. Ferric Chloride, added to a solution of Fe(CN)6 acidi¬ 
fied with HC1, produces a blue precipitate, Fe 4 [Fe(CN)6]3. Decom¬ 
posed by NaOH, forming reddish brown Fe(OH) 3 . (FeS0 4 
produces a white precipitate easily oxidized to a light blue, due 
to the formation of a small amount of ferric salt.) 

3. Insoluble Ferrocyanide.—Solution is accomplished by boil- 

1 Should a cyanide be present HCN would be liberated. 




180 


QUALITATIVE ANALYSIS 


ing with sodium hydroxide. The hydroxide of the metal is pre¬ 
cipitated while sodium ferrocyanide will be in solution. Filter 
off the solution, acidify with HC1 and test for ferrocyanide by 
adding FeCl 3 as stated above. 

FERRICYANIDE, (Fe+ + + (CN) e )- 

Silver Nitrate precipitates reddish brown Ag 3 Fe(CN) 6 , soluble 
in NH 4 OH, and in KCN. 

Ferrous Sulphate, added to a solution of a ferricyanide acidified 
with HC1, forms a deep blue precipitate, Fe 3 (Fe(CN) 6 ) 2 , Turn- 
bulbs blue. Ferric chloride gives a brown color with ferricyanides. 

Ferrous salts should be freshly prepared for the test by dis¬ 
solving pure iron in dilute H2SO4, with exclusion of air. See 
procedure under Iron in Part II, Metals, page 98. 

Note reducing agents, S0 2 , H 2 S, KI, etc., reduce ferricyanides 
to ferrocyanides. 

THIOCYANATE, CN" 

Silver Nitrate precipitates white AgSCN, soluble in an excess 
of NH4OH. 

Ferric Chloride, added to a solution containing SCN acidified 
with HC1, produces a blood-red color due to the compound 
Fe(SCN) 3 . The color disappears upon the addition of HgCl 2 
solution, or Rochelle salts, 



THE ACIDS 


181 


A systematic separation of the acids according to methods used in the 
isolation of the metals has been found impracticable; the following methods of 
| analysis of subgroups will be of value in distinguishing acids closely related. 

Analysis of the Silver Nitrate Group 

Acidify the solution, prepared for acid analysis, with HN0 3 in excess, add 
AgN0 3 . The precipitate that may form indicates the presence of any or all of 
the members of the group. Cl - , Br - , I - , CN - , Fe(CN)e , Fe(CN)e 
in the form of insoluble silver salts. 

Acidify a fresh portion of the solution with HC1 and add a few drops of 
FeS0 4 . 

Blue precipitate forming immediately = Ferricyanide. Confirm. 

White precipitate turning blue =Ferrocyanide. Confirm. 

Test the original substance for HCN and KCNS. 

Detection of Ferro- and Ferricyanide and Thiocyanate in a Mixture.— 

Acidify the solution with HC1, add FeCl 3 in excess, and filter. 

Precipitate.—F«JFe(CN),]„ a Solution.—Red color is due to 

deep blue, Prussian blue. Fe(SCN),. This color may be masked 

!j —-- by the brown color produced by FeCl 3 

acting on Fe(CNV Extract the Fe(SCN) 3 by shaking with a little ether. 
| This will be colored red by the sulphocyanide.__ 

1 To the solution add a few drops of SnCl 2 . The excess of the FeCl 3 is 
reduced and reacts with the ferricyanide, forming the deep blue compound 
Fe 3 [Fe(CN) 6 ] 2 , Turnbull’s blue. ____ 

If CN“ is present with the ferro and ferricyanides, add NaHC0 3 and 
I: distill. Test the distillate for CN according to one of the methods given. 

Caution .—HCN is extremely poisonous. Test in the hood. 

Insoluble double cyanides may be dissolved by boiling with NaOH. 


Detection of Chlorine, Bromine and Iodine 


If cyanogen compounds are present, they should be removed before testmg 


for the halogens. 

Cyanides if present will give a white precipitate 
These may be decomposed by boiling with HN0 3 . 


similar to that of chlorine. 























182 


QUALITATIVE ANALYSIS 


Ferrocyanides and ferricyanides are removed by drying the precipitate in a 
porcelain crucible and heating to dull redness, cooling, and adding a piece of 
zinc and a little H 2 S0 4 . Dilute and filter and add a few drops of HN0 3 and 
AgN0 3 . The halogens will be precipitated free from the cyanides. 


Cyanides may also be removed by taking advantage of the insolubility 
of their nickel or cobalt salts, the halide salts being soluble. Add an excess of 
nickel sulphate and filter. 

Precipitate.— 

Nickel cyanide. 

Filtrate.—Cl", Br - , I“, S0 4 —, Ni+ + . Add NaOH 
drop by drop as long as a precipitate takes place. Filter. 

Precipitate.— 
Ni(OH) 2 .—Reject. 

Filtrate.—Cl“, Br - , I - , etc. Test the halides by 
method of analysis given below. 


Methods for the Separation and Detection of the Halides 


A. Sulphate Method.—Acidify the filtrate, from which the cyanides and 
nickel has been removed, by adding a few drops of H 2 S0 4 , and add ferric sul¬ 
phate (or ferric ammonium sulphate) and boil. 


Violet vapor of I 2 . 


When all of the iodine is expelled, add a cryst 
potassium permanganate and boil. 


tl of 


Brown vapor of Br 2 . 


When the bromine is completely expelled, filter 
and dilute the solution. Silver nitrate now added will 


precipitate white AgCl if chlorine is present. 


B. Persulphate Method.—Neutralize about 10 cc. of the solution with 
acetic acid, adding 1-2 cc. in excess; dilute to six volumes and add about 
half a gram of K 2 S 2 0 8 and heat. Test for free iodine by shaking with CS 2 
(violet). If present, expel by boiling, adding more of the persulphate if 
necessary. (Use casserole and boil 4-5 minutes.) When solution is colorless, 
add more persulphate and boil again to be sure of the complete removal of I, 
Now liberate bromine by adding 2-3 cc. H 2 S0 4 (dilute), and a little more 
K 2 S 2 0 8 , and heat almost to boiling. If the solution is colored yellowish red, 
bromine is indicated. Confirm by testing a few cc. in a test tube with CS 2 
(colored yellow or red). If Br is present, add 0.5 g. more of the persulphate 
to the main solution and expel Br by boiling. The volume of the solution 
should be kept about 60 cc., so that distilled water should be added to replace 
that lost by evaporation. When Br has been expelled, cool and add a few 
drops of AgN0 3 . A white precipitate indicates chlorine. 




















THE ACIDS 


183 


In the presence of chlorates, the halogens should be removed by precipi¬ 
tating with AgN0 3 , filtering, and dissolving the precipitate by means of Zn 
and H 2 S0 4 . This solution may be now tested by the perchlorate method. 

Magenta Test.—The test reagent is made by adding 10 cc. of 0.1 per cent 
solution of magenta to 100 cc. of 5 per cent solution of sulphurous acid and 
allowing to stand until colorless. This is the stock solution. Twenty-five cc. 
of this reagent is mixed with 25 cc. of glacial acetic acid and 1 cc. of sulphuric 
acid. Five cc. of this is used in the test. 

Test.—Five cc. of the magenta reagent is mixed with 1 cc. of the solution 
tested. Chlorine produces a yellow color. Bromine gives a reddish-violet 
coloration. The colored compound in each case may be taken up with chloro¬ 
form or carbon tetrachloride and a colorimetric comparison made with a 
standard. 

In halogen mixes, iodine is first eliminated by heating with an iron per 
salt. Bromine is now liberated by adding sulphuric acid and potassium 
chromate. A glass rod with a pendant drop of sodium hydroxide is held 
in the vapor to absorb bromine, and the drop then tested with the magenta 
reagent. After iodine and bromine are eliminated, chlorine may be tested 
by heating the substance with potassium permanganate, which liberates this 
halogen. 


LABORATORY REVIEW 


1. CIO 3 is removed from a solution of halides on account of its action on 
free iodine. What is this action? 

2. Explain why the difficultly soluble silver halides dissolve in dilute 

sulphuric acid when zinc is added. , 

3. From the solubility table devise a method of separating chlorine from a 


4. ^How can free chlorine in solution be distinguished from combined 

Chl< 5. How would you distinguish between a chloride, a bromide and an 

10d 6. e? Give a procedure for detecting the halides in a mixture containing 
chlorine, bromine and iodine combined as salts. 

7. Give a procedure for detecting H 2 S in an insoluble sulphide. 

8. How can you distinguish (a) A ferrocyanide from a ferncyamde? (b) 

A cyanide from a carbonate? 

9. Give a procedure for testing a thiocyanate. 

10. Study the Table of Reactions—Inorganic Acids—under the Silver 
Nitrate Group, Part V. 


BARIUM CHLORIDE GROUP 


DESCRIPTIVE 


General Characteristics. 

Members of this group are precipitated by BaCl2 from neutral 
solutions. The Sulphate and the Fluoride of Barium are insoluble 
in dilute nitric acid, and in dilute hydrochloric acid. 

Individual Characteristics. 

Arsenous Acid and Arsenic have already been taken up in connnection 
with arsenic in the Soluble H 2 S Subgroup. If arsenic has been found, these 
acids are likely to be present. 

Arsenic Acid.—H 3 As0 4 .—Mol.wt. 151.03; sp.gr. 2.5; m.p. 35.5°; b.p. 
H 3 As0 4 -H 2 0, 160°. The acid dissolves readily in water and alkalies. 

BORON 

B t ii o. { amor P- sp.gr. 2.45; m.p. 2200°; b.p. sublimes. 

, a .w . . , | cryst S p.g r> 2.55; m.p. 2600°; b.p. 3500° C.; oxide, B 2 0 3 . 

Crystalline boron is scarcely attacked by acids or alkaline solutions; the 
amorphous form, however, is soluble in concentrated nitric .and sulphuric 
acids. Both forms fused with potassium hydroxide are converted to potas¬ 
sium metaborate. 

Boric Acid—H 3 B0 3 .—Mol. wt. 62.02; sp.gr. 1.435; m.p. 184°-186°. 

Boracic acid occurs free in the mineral sassolite, and to some extent in 
mineral waters (Tuscany springs). The borates are derived from tetraboric 
acid. Ordinary borax, Na 2 B 4 0 7 • 10H 2 O, is one of its familiar compounds. 
The ortho, H 3 B0 3 , meta, HB0 2 , and tetra or pyro, H 2 B 4 0 7 , respond to the 
same tests. 

Boric acid is more readily soluble in pure water than in hydrochloric, 
nitric, sulphuric, or acetic acids, but more soluble in tartaric acid. It is 
soluble in alcohol and volatile oils. Borax is insoluble in alcohol. With 
acids it becomes transposed to boric acid and the sodium salt of the acid. 

Most borates of the alkalies are soluble in water, and have an alkaline 
reaction due to the slight dissociation of boracic acid. Other borates are not 

184 


THE ACIDS 


185 


readily soluble in water, but dissolve in inorganic acids. Most borates, 
upon heating, expand, then fuse into a transparent form. Only one of the 
hydrogen atoms is replaceable by metals. Most of the boron compounds 
show a great similarity to the corresponding silicon compounds. 


DETECTION 

Flame Test. —Boric acid is displaced from its salts by nearly all acids, 
including even carbonic acid. Upon ignition, however, it in turn drives out 
other acids which are volatile at lower temperatures. A powdered borate, 
previously calcined, is moistened with sulphuric acid and a portion placed on 
the loop of a platinum wire is heated to expel the sulphuric acid, then moistened 
with glycerine and placed in the colorless flame; a green color will be imparted 
to the flame. Copper salts should be removed with H 2 S and barium as BaSO< 
if present, as these also color the flame green. , . 

The flame test may be conveniently made by treating the powdered sample 
in a test tube with sulphuric acid and alcohol (preferably methyl alcohol). A 
cork carrying a glass tube is inserted and the test tube gently warmed. The 

escaping gas will burn with a green flame. 

The test may be made by igniting the mixture of powder, alcohol, and sul¬ 
phuric acid in an open porcelain dish. The green color will be seen m presence 
of a borate. The test is not as delicate as the one with the test tube. 

Borax Bead.— Na 2 B 4 O 7 -10H 2 O fused in a platinum loop, swells to several 
times its original volume as the water of crystallization is being driven out 
to contracts to a clear molten bead. If the bead is dipped into a weak 
solution of cobalt and plunged into the flame, until it again becomes molten, 
the bead upon cooling will be colored blue. , 0 

h Turmeric Test.—A few drops of acetic acid are added together with 2 
or 3 drops of an alcoholic turmeric solution to an alcohohc extract of the 
sample placed in a porcelain dish. The solution is diluted with water and 

thm evaporated to dryness on the water bath. 1/1000 milligram of boric 
then evaporated w y milligram will give a strong reddish- 

i • 1_ ...hat tnnmnPS hlnish-black when treated with a drop 


bluish-black when treated with a drop 

of sodium hydroxide solution. 

CHROMIC ACID AND CHROMATES 

ThP student is referred to the section on Chromium, under the Ammonium 
Sulphide Group, Part II, The Metals, for the review of this element an i s 

acid combinations pages 83, , 9T hoteric electrolyte. Chromic 

s .—*— 

when boiled. 





186 QUALITATIVE ANALYSIS 


Chromic acid forms red needles which decompose in a warm solution’ 
Cr0 3 +H 2 0 resulting. 

Chromates form yellow crystals and color a solution yellow. The chro¬ 
mates of the heavy metals and of Ba are insoluble in water. The alkali 
chromates and the chromates of Mg and Ca are soluble. All chromates 
are transposed by boiling with Na 2 C0 3 . 

Insoluble Chromium Compounds.—These are brought into solution by 
fusing the solid with Na 2 C0 3 and a little KC10 3 . The mass extracted with 
water will give a solution of a chromate and a residue of the metals. 

DETECTION 

All solutions containing chromates are orange or yellow colored. A reduc¬ 
ing agent such as H 2 S, S0 2 , alcohol in presence of an acid produces a green 
color. Warming may be necessary to hasten the reaction. See laboratory 
exercises for tests and reactions, page 194. 

FLUORINE 

F“, at.wt. 19; D (air) 1.31 15 °, sp.gr. (-187°) 1.14; m.p. -223; b.p. -187°C.; 

acids, HF, H 2 SiF 6 . 

Fluorine, F. The univalent element is a greenish yellow poisonous gas. 
It decomposes cold and hot water. It occurs in the minerals fluor spar, 
CaF 2 ; cryolite, 3NaF+AlF 3 and to a slight extent in mineral springs, 
ashes of plants, in bones and teeth as CaF 2 . 

The determination of fluorine in the evaluation of minerals used for the 
production of hydrofluoric acid is of technical importance. The demand for 
elimination of the use of fluorides for preservatives of food makes its detection 
important. 

Fluorides of the alkalies except lithium and of Ag, Al, Hg, Co, Ni, Sb, 
Sn (ous) are readily soluble; copper, lead, zinc, and iron fluorides are sparingly 
soluble; the alkaline earth fluorides dissolve in 100 cc. H 2 0 as follows: 
BaF 2 = 0.163 gram, SrF 2 = 0.012 gram, CaF 2 = 0.0016 gram. 

Fluosilicates of potassium, sodium, and barium are slightly soluble in 
water and practically insoluble if sufficient alcohol is added. 

Fusion of the calcium salt CaF 2 only partially transposes the compound. 
In presence of silica the action may go to completion. 

Hydrofluoric Acid, HF.—Mol. wt. 20.01; sp.gr. 0.71260°; m.p. —92.3°; 
b.p. 19.44°. Hydrofluoric acid is a colorless, mobile liquid which fumes in 
the air. It readily attacks glass, hence must be kept in vulcanite, paraffine, 
or platinum vessels. 


THE ACIDS 


187 


DETECTION OF FLUORIDE 

Fluorine is the most active element known, and is by far the most active 
of the halogens, displacing chlorine, bromine, and iodine from their combina¬ 
tions. 

Etching Test.—The procedure depends upon the corrosive action of hydro¬ 
fluoric acid on glass, the acid being liberated from fluorides by means of hot 
concentrated sulphuric acid. This test is applicable to fluorides that are 
decomposed by sulphuric acid. The reactions taking place may be repre¬ 
sented as follows: 

I. CaF 2 +H 2 SO 4 = CaSO 4 -f 2 HF. 

II. Si0 2 +4HF=2H 2 0+SiF 4 . 

The test may be carried out in the apparatus shown in the illustration 
on this page. A clear, polished glass plate 2 ins. square, free from scratches, 
is warmed and molten wax allowed to 
flow over one side of the plate, the ex¬ 
cess of wax being drained off. A small 
mark is made through the wax, expos¬ 
ing the surface of the plate, care being 
exercised not to scratch the glass. If 
the test is to be quantitative, the marks 
should be of uniform length and width. 

The powdered material is placed in a 
large platinum crucible B (a lead cruci¬ 
ble will do); sufficient concentrated sul¬ 
phuric acid is added to cover the sample. 

The plate (D) with the wax side down 
is placed over the crucible and pressed 
firmly down. To prevent the wax 
from melting, a condenser with flowing 
water, cools the plate. An Erlenmeyer 
flask (C) is an effective and simple form 
of condenser, though a metallic cylinder 
is a better conductor of heat. A little 
water placed on the plate makes better 
contact with the condenser. As a further 
protection a wide collar of asbestos p IG X5.—Etching Test for Fluorine, 
board ( E ) may be placed as shown in 

the figure. In quantitative work, where a careful regulation of heat is neces¬ 
sary, the crucible is placed in a casserole with concentrated sulphuric acid or 




















188 


QUALITATIVE ANALYSIS 


in a sand bath, containing a thermometer to register the temperature. The 
run is best conducted at a temperature of 200 C. (not over 210 H 2 SO 4 
fumes). After an hour the wax is removed with hot water and the plate 
wiped clean, and examined by reflected light for etching. A test is positive 
when the mark can be seen from both sides of the glass. Breathing over the 
etched surface intensifies the mark. 

Treatment of Fluo-Silicates not Attacked by Sulphuric Acid—The pow¬ 
dered material is mixed with about eight times its weight of sodium car¬ 
bonate and fused in a platinum crucible. The cooled melt is extracted with 
water. Calcium fluoride is thrown out from the filtrate. The fluoride may now 
be tested as directed in the etching test or as follows by the hanging drop 
test. 

The Hanging Drop Test.—The test depends upon the reaction 3SiF 4 +3H 2 0 



= 2 H 2 SiF 6 +H 2 SiO 3 . 

If the material contains carbonates, it is calcined to expel carbon dioxide. 

Half a gram of the powdered dry material is mixed with 
0.1 gram dried precipitated silica and placed in a test 
tube, Fig. 16, about 5 cm. long by 1 cm. in diameter. A 
one-hole rubber stooper fits in the tube. A short glass 
tube, closed at the upper end, passes through the stopper 
extending about 3 mm. below. Two or three drops of 
water are placed in this small tube by means of a pipette, 
nearly filling it. Two cc. of concentrated sulphuric acid 
are added to the sample in the test tube and this im¬ 
mediately closed by inserting the stopper carrying the 
hanging drop tube, exercising care to avoid dislodging 
the drop of water. The test tube is placed in a beaker 
of boiling water and kept there for thirty minutes. If 
an appreciable quantity of fluorine is present a heavy 
gelatinous ring of silicic acid will be found at the end of 
the hanging drop tube in the stopper. 

It is important to have material, test tube, and rubber 
stopper dry, so that the deposition may occur as stated. 

Note. —Dr. Olsen makes the test by heating the sample 
in a small Erlenmeyer flask, with concentrated sulphuric 
A watch-crystal with a drop of water suspended on its curved surface 


Fig. 16.—Hanging 
Drop Test for 
Fluorine. 


acid. 


is placed over the mouth of the flask. A spot etch is obtained in presence of 


fluorine. 

Black Filter Paper Test.—According to Browning, small amounts of 
fluorine may be detected by the converse method for detection of silicates 
and fluosilicates (see Silicon). The fluoride is placed with a suitable amount 






THE ACIDS 


189 


of silica, in a small lead cup, 1 cm. in diameter and depth (Fig. 14, page 
161); a few drops of concentrated sulphuric are added; the cup is covered 
by a flat piece of lead with a small hole in the center; upon the cover is 
placed a piece of moistened black filter paper and upon this a small pad of 
moistened filter paper. The cup is heated on the steam bath for ten 
or fifteen minutes. A white deposit will be found on the under side of 
the black filter paper, over the opening in the cover, if fluorine is present 
in an appreciable amount. (0.001 gram CaF 2 and 0.005 gram Na 3 AlF« 
will give test.) 


PHOSPHORUS AND ITS ACID COMBINATIONS 


_ . yellow 1.831 

P 4 , at.wt. 31.04; sp.gr. red 22% ; m.p. 


44 c 
725 c 


5 b-P- 


290°C. 


; oxides, 


P 2 0 3 , P0 2 , P 2 0 5 ; acids, H 3 P0 2 , H 3 P0 3 , H 3 P0 4 , HP0 3 , H 4 P 2 0 7 . 


Phosphoric Acid, H 3 P0 4 .—Phosphorus forms a number of acids—hypo, 
meta, ortho, and pyrophosphoric and hypo, meta, and pyrophosphorous acids. 
Orthophosphoric acid, H 3 P0 4 , is the most stable in solution. The other 
phosphoric acids are converted into the ortho form by boiling with water. 
Mol.wt. 98.02; sp.gr. 1.88; m.p. 38.6°. Orthophosphoric acid is very soluble 
in water. It is a tribasic acid, and has consequently three series of salts. 
The phosphates occur principally as calcium phosphate, Ca 3 (P0 4 ) 2 , in minerals 
and in bones; in iron they occur as Fe 3 (P0 4 ) 2 . Phosphates are found in both 
plants and animals. The phosphates of the alkalies are soluble in water, 
whereas the normal phosphates of the metals are insoluble but are readily 
soluble in mineral acids. 


DETECTION 

Element.—Phosphorus is recognized by its glowing (phosphorescence) in 
the air. The element is quickly oxidized to P 2 0 6 ; if the yellow modification 
is slightly warm (34° C.) the oxidation takes place with such energy that the 
substance bursts into flame. The red form is more stable. It ignites at 
260° C. 

Boiled with KOH or NaOIi it forms phosphine, PH 3 , which in presence of 
accompanying impurities is inflammable in the air. 

Phosphorus oxidized to P 2 O 5 may be detected with ammonium molybdate, 
a yellow compound, (NH 4 ) 3 P0 4 -12Mo0 3 -3H 2 0, being formed. 

Acids. Hypophosphorous Acid, H 3 P0 2 , heated with copper sulphate to 
55° C. gives a reddish-black compound, Cu 2 H 2 , which breaks down at 100° to 
H and Cu. Permanganates are reduced immediately by hypophosphorous 







190 


QUALITATIVE ANALYSIS 


acid. No precipitates are formed with barium, strontium or calcium solutions. 
Zinc in presence of sulphuric acid reduces hypophosphorous acid to phosphine, 
PH 3 . 

Phosphorous Acid, H PO>—Copper sulphate is reduced to metallic copper 
and hydrogen is evolved, no CU 2 H 2 being formed as in case of hypophosphorous 
acid. Permanganates are reduced slowly. Added to solutions of barium, 
strontium or calcium white phosphites of these elements are precipitated. 
Alkali phosphites are soluble in water, while hypophosphites are not readily 
soluble. 

Orthophosphoric Acid, H 3 PO 4 .—Ammonium phosphomolybdate precipi¬ 
tates yellow ammonium phosphomolybdate from slightly nitric acid solutions. 
The precipitate is soluble in ammonium hydroxide. 

Metaphosphoric Acid, HP0 3 .—Converted by nitric acid in hot solutions 
to the ortho form. Metaphosphoric acid is not precipitated by ammonium 
molybdate. 

Pyrophosphoric Acid, H 4 P 2 0 7 .—Converted to orthophosphoric acid in hot 
solutions by nitric acid. No precipitate is formed with ammonium molybdate. 


Comparison of Ortho, Meta and Pyrophosphoric Acids 


Reagen t 

Orthophosphoric 

acid 

Metaphosphoric 

acid 

Pyrophosphoric 

acid 

Ammonium molybdate. 

Yellow ppt. 

No ppt. 

No ppt. 

Albumin . 


Coagulated 

No ppt. 

Not coagulated 

Zinc sulphate, cold, in excess . . . 


White ppt. 

Silver nitrate in neutral solution. 

Yellow ppt., 

White ppt., 

White ppt., 


Ag s P0 4 

AgPO- 

Ag 4 P 2 0 7 

Magnesium salts. 

White ppt. 

No ppt. 

No ppt. 


Phosphorous acids are distinguished from phosphoric acids by the phos¬ 
phine formed with the former when acted upon with zinc. 

Acid phosphates are distinguished from normal phosphates as follows: 
Neutral silver nitrate added to an acid phosphate liberates free nitric acid 
(litmus test), the following reactions taking place: 

3AgN0 3 +Na 2 HP0 4 = Ag 3 P0 4 +2NaN0 3 +HN0 3 . 

The solution resulting when silver nitrate is added to normal phosphate 
solution is neutral. 

3 AgN O 3 +Na 3 PO 4 = Ag 3 PO 4 +3NaNO 3 . 














THE ACIDS 


191 


SULPHURIC ACID, H 2 S0 4 

Mol.wt. 98.09; sp.gr. 1.834; m.p. 10.5°. The acid in its anhydrous solid 
| state forms prismatic crystals. It dissolves in water in all proportions. 

H 2 S 04 -II 2 0 (cone, acid).—Sp.gr. 1.788; m.p. 8.53°; b.p. 210°-338°. 

H 2 SO 4 - 2 H 2 O-Sp.gr. 1.655; m.p. -38.9°; b.p. 170°-190°. 

Sulphuric acid occurs in the free state to a trivial extent in certain volcanic 
springs. It occurs very abundantly combined as sulphates, gypsum, 
CaS 04 - 2 H 2 0 ; barytes, BaS0 4 ; celesite, SrS0 4 , sulphates of the alkalies 
in animal and plant fluids. The acid in pure form is a thick, colorless fluid 
having a great affinity for water. As it is a dibasic acid, it has two series of 
salts. Most of the metals except Pb, Pt, Au, and certain of the rare metals 
are dissolved by dilute sulphuric acid. Most sulphates are soluble in water; 

: those of Ag, Ca, Sr, Pb, and Ba are but slightly soluble in water, the solubility 
decreasing in the order given. Most basic sulphates are insoluble. Na 2 C 03 , 
fused with a sulphate, transposes it into the soluble sodium salt. Ordinary 
boiling with an alkaline carbonate will accomplish this change, but in case of 
BaS0 4 the carbonate is best formed by fusion. Sulphates may be reduced by 
charcoal and fusion mixture to sulphides of the alkalies with exception of the 
alkali and alkaline earth sulphates, most sulphates are decomposed by heat, 
SO3 or S0 2 or both being evolved while the oxide of the metal remains. 

DETECTION 

Sulphate.—A white compound, BaS0 4 , is precipitated in presence of free 
hydrochloric acid when a solution of barium chloride is added to a solution of 
a sulphate. 

Insoluble sulphates are decomposed by boiling or fusion with alkali car- 
! bonates, forming water-soluble alkali sulphates. 

Free sulphuric acid may be detected by evaporating the solution, after 
ji addition of a few grains of sugar, to near dryness. The mixture turns dark 
i as the concentrated acid, when in contact with organic matter, extracts the 
[ elements of water and leaves carbon. 

Note .—For other compounds of sulphur, see pages 162, 168. 






192 


QUALITATIVE ANALYSIS 


LABORATORY EXERCISES 

Reactions—Characteristic Tests 

ARSENITE, As 0 3 , AND ARSENATE, As0 4 

Test.—Acidify and pass in H 2 S. A slight yellow precipitate 
forming slowly indicates an arsenate, AS 2 S 5 . A copious yellow pre¬ 
cipitate indicates AS 2 S 3 , arsenite. 

The student is referred to the section on Arsenic under Metals 
in Part II for tests and reactions. 

Distinction between Arsenite and Arsenate 

(a) Arsenite.— No precipitate is obtained with either ammo¬ 
nium molybdate or with magnesia mixture. Note reaction with 
arsenates. Silver nitrate precipitates yellow silver arsenite, 
Ag 3 As0 3 . (Distinction from arsenate, Ag 3 As0 4 , chocolate brown.) 
Phosphate of silver is also yellow. 

Reaction. —Na 3 As0 3 +3AgN0 3 = 1 Ag 3 As0 3 +3NaN0 3 . 

(b) Arsenate.—Precipitates are obtained with ammonium 
molybdate and with magnesia mixture (distinction from arsenites). 
Similar precipitates are obtained with phosphates. The pre¬ 
cipitate with magnesia mixture, white crystalline NH 4 MgAs0 4 
may be distinguished from NH 4 MgP0 4 by the fact it is 
rendered reddish brown by treatment with AgN0 3 reagent 
(Ag 3 As0 4 formed). The precipitate with ammonium molybdate 
(NH 4 ) 3 As0 4 -12Mo0 3 ) forms more slowly and requires warming 
to a higher temperature for complete precipitation than does 
the phosphate compound. 

Reactions: (a) H 3 As0 4 +12(NH 4 ) 2 Mo0 4 +21HN0 3 = 

i (NH 4 ) 3 As0 4 12Mo0 3 +21NH 4 N0 3 +12H 2 0. 

(6) Na 3 AsO 4 +MgCl 2 +NH 4 C1 = i NH 4 MgAs0 4 +3NaCl. 


THE ACIDS 


193 


Silver Nitrate precipitates chocolate-colored Ag 3 As0 4 when 
added to neutral solutions of arsenates. (Arsenites and phos¬ 
phates of silver are yellow.) 

BORATE, BO 3 

1. Precipitation Test with Barium Chloride—Add the reagent 
to a borate solution. The white precipitate is barium metaborate, 
Ba(B0 2 )2, soluble in excess of the reagent, in acids, and in ammo¬ 
nium chloride. The solution of the borate should be concentrated. 

Reaction.— Na 2 B 4 07+BaCl 2 +3H 2 0 = J, Ba(B02)2+2H 3 B0 3 +2NaCL 

Note. —AgN0 3 added to a concentrated cold solution also gives a white 
precipitate of AgB0 2 soluble in NH 4 OH and in HN0 3 . 

2. Alcohol Flame Test.—Mix a borate in a thin paste with 
concentrated H 2 SO 4 and a little alcohol; on being ignited the 
alcohol is tinged with a green color, due to the volatile compound, 
(C2H 5 )3B()3, being formed. The experiment may be performed 
in a test tube; the solid added and made into a paste with H 2 SO 4 . 
A one-hole stopper, with a glass tube drawn out to capillarity 
at the free end is placed in the test tube upon the addition of a 
little alcohol. When the solution is warmed and the issuing gas 
rejected into the opening at the base of a Bunsen burner, a green 
flame will be produced if a borate is present. 

Reaction.— H 3 B0 3 +3C 2 H 5 0H «=± T (C 2 H 6 ) 3 B0 3 +3H 2 0. 

Note .—Silicates containing boron are decomposed by adding a little 
calcium fluoride and sulphuric acid, BF 3 is volatilized on heating and colors 
the Bunsen flame green. 

3. Turmeric Test.—Moisten a portion of a piece of turmeric 
paper with an acidified (HC1) solution of a borate, and dry on a 
watch glass. The portion moistened is colored brownish red or 
pink. A drop of NaOH causes this to change to a greenish brown 
or black. The unmoistened portion serves as a control. 








194 


QUALITATIVE ANALYSIS 


Notes —Oxidizing agents such as chlorates, iodides, chromates, destroy 
the turmeric, hence should not be present. HNOs does no harm. HC10 3 
and H 2 Cr0 4 may be reduced in dilute HC1 solution with Na2S0 3 . 

FeCl 3 colors the turmeric paper brown. 

4. Borate Ignited.—Dip a platinum wire with loop into water 
and then into powdered borax. Place in a flame and note that 
the salt swells (escape of water) and then fuses in a clear bead. 
If the bead is moistened with a solution of cobalt salt and again 
heated a blue-colored bead is obtained. 

Na 2 B 4 0 7 + CoO = Co (BO2)2 (blue) +2NaB0 2 . 

CHROMATE, 1 Cr0 4 — 

1. Chromate and chromic acid have been mentioned under 
chromium. (See Ammonium sulphide group, page 83, 94.) 
Chromates are all red or yellow. The acid solutions are red 
(dichromate) and the alkaline solutions yellow (chromate). The 
color is evident in very dilute solutions and is characteristic 5 a 
colorless solution, therefore, does not contain a chromate. 

Determine the sensitiveness of the color test for a chromate, 
using K 2 Cr 04 . See page 210—Reaction Limits. 

2. Reducing Agents change yellow chromates into green chro¬ 
mium salts, e.g., from acidic to basic chromium. To an acid 
solution of a chromate add a little alcohol and boil. Note the 
change of yellow to green. 

Reaction. —K 2 Cr 2 07 (orange) -J-3C 2 H50H+8HC1 = 2CrCl 3 (green) 

+ T 3H 3 CHO+2KC1+7H 2 0. 

3 . Hydrogen Peroxide.—Acidify a very dilute solution of H 2 O 2 
with dilute H 2 S0 4 . Add about 4 cc. of ether and then a few drops 
of a dilute chromate solution. A blue coloration is produced by 
chromate or dichromate. On shaking, the ether takes up the 
blue compound (HCr0 4 ), forming a brilliant blue layer. 

1 See Descriptive Section for Insoluble Chromium Compounds. 


THE ACIDS 


195 


4. Barium Chloride Test.—Add the reagent to an acidified 
(HN0 3 ) solution of a chromate together with 4-5 cc. of NaC 2 H 3 0 2 
solution; the yellow precipitate is BaCr0 4 . Write out reaction. 

Note. If S0 4 ~, PO 4 , Cr (>4 , or C 4 H 4 O 6 are present, make 

alkaline with NH 4 OH and add 1-2 cc. of CaCk and shake. Filter after 
10-15 minutes. Acidify filtrate with HNO a and test for chromate. 

5. Lead Acetate Test.—Add the reagent to a solution of 
K 2 Cr0 4 . The yellow precipitate is PbCr0 4 . Write the reaction. 

6 . Silver Nitrate Test.—The reagent added to a neutral solu¬ 
tion gives the purplish-red silver chromate, soluble in HNO3 and 
in NH 4 OH. The reddish-brown dichromate is precipitated from 
concentrated solutions, faintly acid. Write out reactions with 
K 2 Cr0 4 and K 2 Cr 2 C> 7 . 

FLUORIDE, F 

Use an alkali fluoride for the tests. 

1. Precipitation Tests, (a) Barium Chloride. —Add the reagent 
to the solution of a fluoride. The white precipitate is BaF 2 . Test 
solubility in HC1 or HNO 3 . Does the precipitate dissolve in a 
solution of NH 4 C1? 

(h) Calcium Chloride. —To an aqueous solution of a fluoride 
add CaCl 2 solution. The white precipitate is CaF 2 . The com¬ 
pound is difficultly soluble in HNO 3 and in HC1. It is practically 
insoluble in acetic acid. 

Reaction. —2KF+CaCl2 = i CaF 2 (white) +2KC1. 

2 . Etching Tests.—Consult “ Detection ” of Fluorides under 
the descriptive section for Fluorine, page 187. 

(а) Action of H 2 S0 4 on a fluoride. 

CaF 2 +H 2 S0 4 = i CaS0 4 + T2HF. 

Silica in glass is acted on as follows: 

Si0 2 +4HF = t SiF 4 +2H 2 0. 

(б) Action of H 2 0 on SiF 4 : 

3SiF 4 +4H 2 0 = i H4Si0 4 +2H 2 SiF 6 . 




196 


QUALITATIVE ANALYSIS 


PHOSPHATE, P0 4 - 

1. Ammonium Molybdate Test.—Add the reagent to a solution 
of a phosphate acidified with HNO 3 and warmed to 40°, a yellow 
precipitate of (NH 4 ) 3 P0 4 - 12Mo0 3 is formed. Arsenic produces 
a similar precipitate, but a higher temperature is necessary for 
complete precipitation. 

2. Magnesium Mixture, (MgCl 2 +NH 4 Cl+NH 40 H).—Add 

the reagent to a solution of orthophosphate. The white crystal¬ 
line precipitate is ammonium magnesium phosphate (NHUMgPCU • 
6H 2 0). 

Reaction.—MgCl 2 +Na 2 HP0 4 +NH 4 0H = i NH 4 MgP0 4 +2NaCl+H 2 0. 

The precipitate is soluble in acids, including acetic acid. It 
is slightly soluble in water but insoluble in dilute NH4OH. 

Arsenates also gives a precipitate with magnesia mixture. 
The phosphate treated with AgN0 3 , however, turns yellow, while 
the arsenate changes to a reddish brown color. 

3. Barium Chloride precipitates white BaHPCU from neutral 
solutions. The precipitate dissolves in acids (HN0 3 , HC1, 
HC 2 H 3 0 2 ). If NH 4 OH is added to this acid solution Ba 3 (PC> 4)2 
is precipitated. 

Reactions.— (a) Na 2 HP0 4 +BaCl 2 = f BaHP0 4 +2NaCl. 

(6) BaHPO 4 +2HC1 = BaCl 2 +H 3 PO 4 . 

(c) (3BaCl 2 + 2H 3 P0 4 ) +6NH 4 OH = [ Ba 3 (P0 4 ) 2 +6NH 4 Cl 
+6H 2 0. 

4. Ferric Chloride added to a soluble phosphate slightly acid 
with HC1 precipitates light yellow ferric phosphate. In presence 
of the acid the reaction is reversible. By adding sodium acetate 
the precipitation is complete, since FeP 04 is insoluble in acetic 
acid. 

Reactions. —(a) Na 2 HP0 4 +FeCl 3 = f FeP0 4 +2NaCl+HCl. 

(6) Na 2 HP0 4 +FeCl 3 +NaC 2 H 3 0 2 = | FeP0 4 +3NaCI 
+HC 2 H 3 0 2 . 



THE ACIDS 


197 


The reaction has been considered in the study of the metals 
of the Ammonium Sulphide Group. The procedure being used 
for removal of phosphoric acid, which interferes in the detection 
of members of this group. 

5. Silver Nitrate precipitates yellow Ag 3 P0 4 from neutral 
solutions of orthophosphates soluble in acids and in ammonia. 

2Na 2 HP0 4 +3AgN0 3 = j Ag 3 P 04 +NaH 2 P 04 + 3 NaNC> 3 . 

6. Lead Acetate precipitates white Pb 3 (P0 4 )2, very slightly 
soluble in acetic acid, readily soluble in nitric acid. 

2 Na 2 HP 04 + 3 Pb(C 2 H 3 0 2 )2 = j Pb 3 (P 0 4 ) 2 + 4 NaC 2 H 30 2 + 2 HC 2 H 3 0 2 . 

SULPHATE, S0 4 — 

1. Barium Chloride precipitates white BaS0 4 from a solution 
j containing a sulphate. The heavy precipitate is insoluble in 
dilute mineral acids. BaS0 4 is soluble in strong LGSCU, repre- 
| cipitated on dilution. 

Reaction.— H 2 S0 4 +BaCl 2 = l BaS0 4 +2HCl. 

! The precipitation is conducted in presence of free nitric or 
hydrochloric acid to prevent precipitation chromates, carbonates 
! and sulphites. 

Selenium may be mistaken for sulphur. White BaSe0 4 is precipitated 
I from the acid (HC1) solution of selenic acid H 2 Se0 4 or its salts. BaSe0 4 
; is distinguished from BaS0 4 by the fact that boiling it with strong HC1 causes 
its solution and chlorine gas is evolved, while BaS0 4 is unchanged. 

* 2. Lead Acetate precipitates white PbS0 4 , soluble in 

! NH 4 C2H 3 02, KOH, and in ammonium tartrate. 

Reaction.— H 2 S0 4 +Pb(C 2 H 3 0 2 ) 2 = j PbS0 4 +2HC 2 H 3 0 2 . 

3. Reduction Test.—A sulphate fused with Na 2 C0 3 and organic 
substance or free carbon (starch, sugar, charcoal, etc.) is reduced 
to a sulphide. Test for H 2 S by one of the procedures given 
for this compound on page 167. Other sulphur compounds also 
form sulphides. 





198 


QUALITATIVE ANALYSIS 


Analysis of the Barium Chloride Group 

To the neutral solution prepared for acid analysis (Part IV) add BaCla and 
CaCl 2 . If a precipitate does not form, the group is absent. (Silica may be 
present in the original substance, owing to its insolubility. The slight solu¬ 
bility of the calcium and barium borates may prevent the precipitation of 

boric acid.) . . 

If a precipitation occurs, test for the members individually. Chromates 

are present only in colored solutions. 

In testing for phosphoric acid, make tests first for arsenites and arsenates, 
since confusion of interpretation will result, owing to similarity of reactions. 
Unless the method of preparation of the solution (Part IV) has removed arsenic 
this should be done by passing H 2 S into the acidulated solution (HC1) as long 
as a precipitate forms, and filtering off the sulphide. The solution can now 
be tested for phosphates after first expelling the H 2 S. 

Separation of Arsenates and Arsenites and Phosphates.—To the solution 
add an excess of magnesia mixture, shake, and allow to stand 6-10 minutes, 


filter and wash once. 

Precipitate.—MgNH 4 P0 4 and 

MgNH 4 AsC> 4 , white. Dissolve the 
precipitate in HC1, heat to boiling and j 
pass in H 2 S as long as a precipitate 
forms. (It is advisable to reduce arsen 
the H 2 S by boiling with Na 2 SO,j.) 

Filtrate.—Arsenites. 

Acidify with HC1 and pass in H 2 S. 
A copious yellow precipitate is As 2 S3. 

ic to arsenous form before passing in 

Precipitate.—AS 2 S 3 or AS 2 S 5 , yellow. 

Filtrate.—PO 4 . Test with ammo¬ 
nium molybdate solution for phos¬ 
phates. 












THE ACIDS 


199 


CLASSROOM EXERCISES 

1. In the preparation of the acid solution by the addition of Na 2 C0 3 a 
precipitation generally takes place. Of what general class of substances is it 
apt to be composed? 

2. How can phosphorus or sulphur be detected in an alloy? 

3. Give a method by which BaS 04 or an insoluble silicate may be rendered 
soluble. 

4. In precipitating arsenic acid why is it necessary to acidify with HC1? 

5. Give a method by which a chromate, an oxalate, and a sulphate may be 
separated. 

6. How would you distinguish between: 

(а) A sulphate and a selenate of barium? 

(б) An arsenite and an arsenate? 

(c) A chromic salt, a chromate and a dichromate? 

(d) A sulphate and a sulphite? 

( e) A sulphite and a thiosulphate? 

(/) Magnesium ammonium arsenate and magnesium ammonium 
molybdate? 

(g) Fluoride and fluosilicate? 

7. How can you prove the presence of free sulphuric acid in a solution? 

8. How would you test for the acid radical in CaF 2 ? 

9. What is the action between SiF 4 and H 2 0? 

10. Study the Table of Reactions for Inorganic Acids under the column of 
Barium Chloride Group, Part V. 




SOLUBLE ACID GROUP 

DESCRIPTIVE 

General Characteristics. 

The members of this group are not precipitated by BaCk nor 
by AgN 03 . 

Individual Characteristics. 

CHLORIC ACID, HCIO, 

Only the aqueous solution containing 40 per cent of HCIO 3 is known. 
It is a thick colorless liquid which readily decomposes into Cl+O and per¬ 
chloric acid, HClOi. It is a very active oxidizing agent. Chlorates readily 
give off the oxygen, decomposing with explosive violence when rubbed or 
heated with oxidizable bodies, such as P, S, Sb 2 S 3 sugar, etc. All chlorates 
are soluble in water. With prolonged ignition chlorates are decomposed 
liberating oxygen and leaving a residue of the chloride salt. 

Detection of Chlorate.—The dry salt heated with concentrated sulphuric 
acid detonates and evolves yellow fumes. 

Chlorates liberate chlorine from hydrochloric acid. 

Perchlorate.—The solution is boiled with hydrochloric acid to decompose 
the hypochlorite, chlorite and chlorate. The Chlorides is removed by precip¬ 
itation with silver nitrate, the filtrate evaporated to dryness, the residue fused 
with sodium carbonate to decompose the perchlorate to form the chloride, 
which may now be tested as usual. 

See tests under Laboratory Exercises, page 203. 

NITROGEN 

Element, N 2 , at.wt. 14.01; D. (air) 0.9674; m.p. -210°; b.p. -195.6° C.; 
oxides, N 2 0, N 2 0 2 , N 2 0 3 , N 2 04 , N 2 Os. 

Occurrence. Element.—It occurs free in air to extent of 78 per cent by 
volume and 76 percent by weight. 

Nitrogen is found combined in nature as potassium nitrate (saltpeter), 
KN0 3 ; sodium nitrate (Chili saltpeter), NaN0 3 , and to a less extent as 
calcium nitrate, Ca(N0 3 ) 2 . It occurs in plants and in animals, in the sub- 

200 



THE ACIDS 


201 


! stances proteids, blood, muscle, nerve substance, in fossil plants (coal), in 
1 guano, ammonia and ammonium salts. 

Compounds of ammonia and of nitric acid are generally soluble in water. 
All nitrogen compounds, however, are not included. Among those which 
are not readily soluble the following deserve mention: compounds of nitrogen 
in many organic substances; nitrogen bromophosphide, NPBr2, nitrogen 
selenide, NSe; nitrogen sulphide, N 4 S 4 ; nitrogen pentasulphide, N 2 S 6 ; 
ammonium antimonate, NH 4 Sb0 3 -2H 2 0; ammonium iodate, HN 4 I0 3 
(2.6 grams per 100 cc. H 2 0); ammonium chlorplatinate, (NH 4 ) 2 PtCl 6 (0.67 
gram); ammonium chloriridate, (NH 4 ) 2 IrCl 6 (0.7 gram); ammonium oxalate, 
(NH 4 ) 2 C 2 04*H 2 0 (4.2 grams); ammonium phosphomolybdate, (NH 4 ) 3 P0 4 - 
12Mo0 3 (0.03 gram); nitron nitrate, C 20 Hi 6 N4-HNO 3 . 


DETECTION 

Element. Organic Nitrogen.—Organic matter is decomposed by heating 
in a Kjeldahl flask with concentrated sulphuric acid whereupon ammonium 
sulphate is formed. Ammonia may now be liberated from the sulphate and so 

^Nitrogen in Gas.— Recognized by its inertness towards the reagents used 
in gas analysis. The element may be recognized by means of the spectroscope. 

NITRIC ACID 

HNO3, m.w., 63.02; sp.gr. 1.53; m.p. -41.3; b.p. 86° C. 

' Boiling-point of commercial 95 per cent acid is a little above 86°, but gradu¬ 
ally rises to 126° and the strength of acid falls to 68.9 per cent, sp.gr is then 
1 42 The acid now remains constant, the distillate being of the same strength. 

The acid radical occurs in nature in the form of nitrates m sodium nitrate 
Chili saltpeter, NaN0 3 ; potassium nitrate, KN0 3 ; and Ca(N0 3 ) 2 , wall 
saltpeter. Nitrates are formed in all decomposition processes of organic 
nitrogenous substances. Nitrates are all soluble in water, except a few bas c 
nitrates such as BiONO s , etc. Most nitrates are deliquescent except those 
of Ag, Pb, Sr, Ba, Na, K, NH 4 . Boiling with sodium carbonate forms sodium 

nitrate. 

detection of nitric acid and nitrates 

Nitrates are detected by the brown color produced by the action of a 
saturated sulphuric acid solution of ferrous sulphate on a nitrate solution 

stronglv acid with H 2 S0 4 . . , 

With diphenylamine reagent nitrates give a blue color. 

* See tests under Laboratory Exercises, page 203. 






292 


QUALITATIVE ANALYSIS 


For detection of nitrous acid and nitrites, see subject under the Volatile 
Acid Group, pages 159, 165. 

PERMANGANIC ACID, HMn0 4 

This acid is known only in its aqueous solutions and in the form of its 
salts, i.e., KMnOi, NaMnCh, etc. The permanganates are all soluble in water, 
forming purple solutions. Like the chlorates, they are good oxidizing agents. 
They liberate chlorine from hydrochloric acid and oxidize ferrous salts to 
ferric, sulphur dioxide to sulphuric acid, oxalic acid to CO 2 and H 2 O. 

Reaction, Acid Solution.— 2KMn0 4 +3H 2 S0 4 in presence of reducing 
agent = K 2 S0 4 +2MnS0 4 +3H 2 0+50. 

Alkali Solution.—2KMnO 4 +H 2 0 = 2MnO 2 +2KOH+30. 

Detection.—Permanganate solutions are pink or red according to the 
concentration of the solutions. 

Permanganates are reduced by H 2 S to manganous salts. The tests for 
manganese have been given in Part II under the Ammonium Sulphide Group, 
pages 88 and 103. 


THE ACIDS 


203 


LABORATORY EXERCISES 

Reactions—Characteristic Tests 
CHLORATE, CIO^T 

1. Sulphuric Acid, concentrated, decomposes chlorates with lib¬ 
eration of CIO 2 greenish-yellow gas. The unstable CIO 2 decom¬ 
poses on warming. This is evident by the fact that when strong 
H 2 SO 4 is added to the dry salts an explosion results, with slight 
warming of the mixture. Make the test by placing strong H 2 SO 4 
in a test tube, drop in a crystal of KCIO 3 and warm gently over a 
low flame. 

Reaction.—3KC10 3 +2H 2 S0 4 = T2C10 2 +KC10 4 +2KHS0 4 +H 2 0. 

2. Oxidizing Action.—Chlorates react with strong HC1 liberat¬ 
ing CIO 2 and Cl and forming a chloride. 

Reaction.—KC10 3 +2HC1 = | C10 2 + t C1+KC1+H 2 0. 

3. Reducing Agents.—Add an alkali sulphite to a chlorate 
solution and acidify with H2SO4. The SO2 reduces the chlorate 
to a chloride. 

HCIO 3 +3SO 2 +3H 2 0 = 3H 2 SO 4 +HC1. 

4. Aniline Sulphate Test.—To a solution of chlorate in cold 
cone. H 2 SO 4 add a drop of aniline sulphate. A deep blue color is 
developed. The color becomes more intense by adding a few 
drops of water. 

NITRATE, N0 3 - 

1. (a) Ferrous Sulphate Test.—When concentrated nitric acid 
is added to a solution of ferrous sulphate, the ferrous salt is oxidized 
to Fe 2 (S0 4 )3 and NO is formed. The oxide of nitrogen unites 
with the unchanged ferrous sulphate, forming a brown unstable 
compound (FeS 04 ) 2 N 0 . 

About 1-2 cc. of the concentrated solution of the substance 
is added to 15 to 20 cc. of strong sulphuric acid in a test tube. 






204 


QUALITATIVE ANALYSIS 


After cooling the mixture, the test tube is inclined and an equal 
volume of a saturated solution of ferrous sulphate is allowed to 
flow slowly down over the surface of the acid. The tube is now 
held upright and gently tapped. In the presence of nitric acid a 
brown ring forms at the junction of the two solutions. 

(b) A nitrate may be tested by adding to the solution sufficient 
sulphuric acid to make it strongly acid and then a large excess of 
a saturated solution of ferrous sulphate and sulphuric acid. A 
pink to brown color is obtained, depending upon the amount of 
nitrate present. A quantitative method has been worked out 
from this test. The brown color is permanent when an excess 
of the ferrous salt is present, since free nitric acid fades the 
color. 

Reaction.—2HN0 3 +3H 2 S0 4 +6FeS0 4 = 2NO +3Fe 2 (S0 4 ) 3 +4H 2 0 
and NO+2FeS0 4 = (FeS0 4 ) 2 N0 brown. 

Interfering Substances.—Nitrites give the same test as (a). These do 
not interfere in test ( b ) if present in comparatively small amount. 

Iodides and bromides are liberated by concentrated H 2 S0 4 . These may 
be removed by adding a solution of Ag 2 S0 4 or AgC 2 H 3 0 2 and filtering. 
The filtrate contains the nitrate; the residue is AgBr and Agl. 

Ferrocyanides and ferricyanides form blue compounds with FeS0 4 , which 
mask the brown ring. They may be removed by adding H 2 S0 4 to acidity 
and then FeCl 3 and FeS0 4 , heating to boiling and adding BaCl 2 . The 
residue contains the cyanides and BaS0 4 . Test the filtrate for nitrates. 

Chromates , permanganates , and chlorates interfere, the first two on 
account of their color, the latter because of the violent action that takes 
place when concentrated sulphuric acid is added. They may be removed 
as follows: add Na 2 S0 3 in a porcelain dish and introduce a small portion 
of the original substance and add dilute HC1, warm gently until all excess 
of S0 2 is expelled, filter, and refect the residue. If the filtrate is still 
colored, add Na 2 C0 3 until effervescence ceases, boil 2-3 minutes, dilute and 
filter. The filtrate is used for the nitrate tests. 

2. Phenol Sulphonic Acid Test for HN0 3 .—Evaporate a few 
drops of the solution (freed from chromates, permanganates, 
chlorates, and ferro and ferricyanides) to dryness in a porcelain 


THE ACIDS 


205 


crucible, cool the residue, and add 2-3 cc. of the reagent 1 and 
warm gently; now add NH 4 OH. The deep yellow ammonium 
picrate is formed if nitrates are present. Iodine and bromine 
do not interfere with this test. This method is used in water 
analysis in quantitative tests for nitrates. 

3. (a) Reduction Test.—Dissolve in the solution a small 
crystal of KI and then add a drop of starch solution and 2 cc. of 
dilute H 2 SO 4 and a small piece of zinc. If nitrates are present, a 
blue color will result, first appearing around the zinc. 

The H liberated reduces HNO 3 to HN0 2 , and the latter 
liberates free I, causing the starch to be colored. CS 2 may be 
used in place of the starch. Further reduction will liberate 
ammonia which can be recognized by its odor. See (6). 

(b ) Reduction to Ammonia. —Make the nitrate solution 
strongly alkaline with NaOH and add metallic filings of aluminum, 
or zinc or iron and heat. Note the odor of NH3 due to the reduc¬ 
tion of HNO3. Nitrites also are reduced to NH3. 

4. Diphenylamine Test.—To 2 cc. of the solution containing the 
nitrate, placed on a watch glass, add 5 cc. of the reagent made by 
dissolving 5 mg. of diphenylamine, (C 6 H 5 ) 2 NH, in 100 cc. of cone. 
H 2 S04- Warm gently. A blue color develops in presence of 
nitrates. Cl, Cl v , Br v , I v , Mn vn , Cr VI , Se IV , and Fe™ interfere. 

5. Free HNO3. —(a) Copper filings placed in a hot solution of 
HNO 3 cause the evolution of brown fumes. 

3Cu+8HN0 3 +0 2 (air) = T 2N0 2 +3Cu(N0 3 ) 2 +4H 2 0. 

(b) The solution evaporated to dryness with addition of a 
quill cutting will color the quill yellow. (Xanthoproteic acid is 
formed.) 

PERMANGANATE, Mn0 4 ~ 

1. A permanganate colors a solution red. It may be made 
colorless by reduction to Mn0 2 in an alkaline solution and to 
1 Reagent contains 1 part phenol (cryst. carbolic acid), 4 parts strong 
H 2 S0 4 and 2 parts H 2 0. 


206 


QUALITATIVE ANALYSIS 


manganous salt in an acid solution by reducing agents such as. 
H 2 S, FeS0 4 , H2C2O4, S0 2 . 

Hydrogen 'peroxide decolorizes a permanganate, acidified with 
sulphuric acid, with the evolution of oxygen. 

See section on Manganese under the members of the Ammo¬ 
nium Sulphide Group, Part II on Metals, page 88, 103. 

Analysis of the Soluble Acid Group 

If the solution is colored red, a permanganate is indicated. Decolorize by 
adding H 2 0 2 . 

Evaporate a portion of the solution on the water bath to dryness and test 
the residue for chlorate. 

If a chlorate is present, to a second portion add sodium sulphite (to 
reduce the chlorate) and boil. Cool and test for nitric acid. 

CLASSROOM REVIEW 

1. What is the effect of concentrated sulphuric acid on a chlorate? 

2. What is the effect of hydrochloric acid on a permanganate? 

3. How can you distinguish free nitric acid from a solution of its salt? 

4. Devise a method for separating the acid radicals: C0 3 -- , I - , and 

N °3 • , . . _ 

5. (a) How can you distinguish between mtrates and nitrites? 

(b) In the catalytic oxidation of ammonia to nitric acid both nitric 
acid and nitrous acid are present in the dilute aqueous solution. How can 
you detect the latter in presence of the former? 


ORGANIC ACID GROUP 
DESCRIPTIVE 

General Characteristics. 

The acids of this group (except oxalic acid) char when heated 
to redness. All organic acids contain the carboxyl groups— 
COOH~. The number of these carboxyl groups determines the 
valency of the acid,—monobasic acetic acid, H + CH 3 COO“; 
/COO— 

dibasic oxalic acid 2 H + { . Letting R represent the com- 

^COO 

plex radical, the acids dissociate into H — R* (COO). The potas¬ 
sium and sodium salts of nearly all organic acids are soluble. 
Organic acids occur free or combined as salts of the alkalies and 
other metals together with inorganic salts. Tests should be made 
with the alkali salts or by neutralizing the free acids with an alkali 
carbonate. Only a few of the acids will be studied here. A list 
of additional organic acids and their tests is given in Part V. 

Individual Characteristics. 


ACETIC ACID 

HC 2 H 3 O 2 .-Mol.wt. 60.03; sp.gr. 1.06; m.p. 17°; b.p. 118°. This acid 
occurs in both the animal and the plant kingdoms, free and also combined. 
When not free it is found as calcium or potassium acetate. In pure form at a 
temperature below 17° it forms a clear colorless mass. It produces blisters 
on the skin. It dissolves many organic substances, also S and P. Acetates 
are readily soluble in water, except those of Ag, Hg, and certain basic salts. 
On heating they decompose and leave a residue. The hydroxides of certain 
metals are precipitated when their acetates are boiled. Acetates are trans¬ 
posed by boiling with Na 2 C0 3 . 

On heating acetates decompose with the production of a combustible gas 
and practically no charring. 


207 


208 QUALITATIVE ANALYSIS 

Dilute H2SO4 liberates acetic acid from its salts and may be recognized by 
its odor. 

Ferric chloride colors neutral solutions of acetates brown, on dilution of the 
solution and boiling the iron is precipitated as the red basic acetate. 

Free acetic acid may be recognized by its odor. 

OXALIC ACID 

H 2 C 2 0 4 -2H 2 0. —Mol. wt. 126.05; sp. gr. 1.65; m.p. 98°. Readily soluble 
in alcohol. Most oxalates, except those of the alkalies, and Mg, are not 
readily soluble in water, but soluble in mineral acids. They form sodium 
salts when boiled with Na 2 C0 3 . Oxalates occur in both animal and plant 
kingdoms. 

On heating oxalates are decomposed with evolution of CO and C0 2 . 
Little or no charring occurs. Magnesium oxalate yields MgO on heating. 
Other oxalates leave a residue of the metal or an oxide. 

BaCl 2 precipitates barium oxalate, soluble in oxalic and acetic acids. 

CaCl 2 precipitates white calcium oxalate insoluble in oxalic acid, ammo¬ 
nium oxalate, acetic acid, but soluble in mineral acids. 

AgN0 3 precipitates white silver oxalate, slightly soluble in water. Sol¬ 
uble in ammonia and in nitric acid, 

SALICYLIC ACID 

H 2 C 7 H 4 0 3 . —Mol. wt. 138.05; m.p. 159°; b.p. sublimes. Colorless 
needle-shaped crystals, odorless. Very slightly soluble in water; readily 
soluble in ether and alcohol. Soluble in sodium carbonate. Most of the salts 
of the acid are soluble in water. These are decomposed by dilute mineral 
acids, the salicylic separating out as a white crystalline precipitate. 

TARTARIC ACID 

H 2 C 4 H 4 Oo. —Mol. wt. 159; sp.gr. 1.667; m.p. 1.40°. Rectangular crystals. 
It forms acid and neutral salts, being dibasic. The normal salts with the 
alkalies and most of the salts with the metals of the iron group are readily 
soluble in water. Other normal salts are mostly insoluble. The acid salts 
of potassium and ammonium are difficultly soluble. Tartrates char on heat¬ 
ing. Inflammable vapors are evolved, having an odor of burning sugar. 

Concentrated H 2 S0 4 heated with tartaric acid causes charring with evo¬ 
lution of S0 2 . 

An additional list of organic acids and their tests will be found on pages 
260 and 261. 


THE ACIDS 


209 


LABORATORY EXERCISES 

Reactions—Characteristic Tests 

The student is referred to the Tables of Reactions for tests of 
Organic Acids, Part V, for additional exercises in the study of this 
group. 

ACETATE, C 2 H 3 0 2 - 

1 . Sulphuric Acid Test.—Acetic acid is liberated from its salts 
when warmed with cone. H 2 S0 4 . It can be recognized by its 
odor (vinegar). A little alcohol added forms ethyl acetate, 
C 2 H 5 (C 2 H 30 2 ), which has a characteristic pleasant odor. 

2. Ferric chloride added to a neutral solution of an acetate 
forms a deep red color. If this solution is diluted and boiled, 
Fe( 0 H) 2 -C 2 H 30 2 , red, is precipitated, leaving a clear liquid above. 

OXALATE, C 2 0 4 — 

1. Calcium sulphate solution added to an oxalate solution 
acidified with acetic acid will precipitate white CaC 2 04 . 

Further Confirmation. —Filter, wash and dissolve in a little 
dilute sulphuric acid and add a drop of KMn0 4 . If the perman¬ 
ganate is decolorized, it is due to the reducing action of the oxalate. 

SALICYLATE, C 7 H 4 0 3 — 

1 . Ferric chloride produces an intense violet-red color with 
both salicylic acid and salicylates. This color is destroyed by 
excess of mineral acids and by a large excess of most organic 
acids, but is restored by neutralizing the acid with ammonia. 

2. Nitric acid (cone.) when heated with salicylic acid or its 
salts forms picric acid, yellow: the yellow color is intensified by 
addition of an excess of NaOH. 

TARTRATE, C 4 H 4 O 0 — 

1. Sulphuric acid, cone., causes an effervescence, when added 
to a tartrate and gives off an odor of burnt sugar. The acid is 
darkened due to charring. 







210 


QUALITATIVE ANALYSIS 


2. Silver Nitrate, in faintly ammoniacal solution, heated in a 
clean test tube with a tartrate, is reduced to metallic silver, which 
forms a mirror on the glass. 

Analysis of the Organic Acids 

Test a portion for oxalates by adding CaS0 4 . A precipitate indicates an 
oxalate. The precipitate treated with dilute acetic acid is insoluble and does 
not effervesce. Distinction from carbonate. 

Evaporate almost to dryness. If an oxidizing agent is present, reduce by 
means of S0 2 or H 2 S during the evaporation. Test a portion of the concen¬ 
trated solution for acetic acid. Test another portion for tartaric acid. 

CLASSROOM EXERCISES 

1 . State the uses made of the three acids studied in this group. 

2. Give a scheme of analysis leading to the detection of the following if 
present in a solution: sulphite, arsenite, thiosulphite, sulphate, bromide, iodide, 
ferrocyanide, acetate. 

3. How would you detect a chloride in the presence of a sulphide? 

4 . How would you detect a nitrate in the presence of a ferricyanide? 

5 . How would you distinguish an organic acid from an inorganic acid? 

STUDIES OF REACTION LIMITS 

This is a study of typical reactions to ascertain approximately 
the conditions and concentration necessary for a given substance 
in order to obtain a discernible test of its anion or cation. The 
student should take a normal solution of the substance and dilute 
portions to to N, 5 V N, N, N, 5 ttt N, 10 W N. To these 
solutions, in separate test tubes, add, drop by drop, the precipi¬ 
tating reagent, the strength of which is known. Determine the 
dilution limit at which the ion may be recognized. Does heating 
render the reaction more or less delicate? Calculate the approxi¬ 
mate amount of salt necessary in a hundred cc. of the solution^to 
enable the detection of its ions. 



PART IV 


SYSTEMATIC ANALYSIS OF A SUBSTANCE 

Preliminary Examination of a Solid 

Physical Examination and Dry Tests of the Solids— Object.— 
A preliminary examination is made in order to gain some knowl¬ 
edge of the character of the substance before putting it into 
solution. The process of analysis is frequently shortened by the 
physical examination of the solid and by a few preliminary chemi¬ 
cal tests. The appearance, crystalline form and color of the solid 
substance, changes on exposure to the air, chemical changes due 
to decomposition when heated or treated with certain reagents, 
oxides formed causing color changes, or the color and odor of 
gases evolved, color of oxide with the borax bead, flame tests, 
reduction tests on charcoal, etc., give valuable indications of a 
number of compounds and elements. 

Certain substances, furthermore, must be tested for in the 
original substance—for example, ammonia. Then, again, since 
oxidizing and reducing agents are used during the course of 
analysis, metals having two valences will undergo a change, so 
that in order to find out in what form they exist in the substance 
it is necessary to examine the original compound by special tests. 

In making an analysis, the chemist should bear in mind the 
amount of substance he has at his disposal, and leave a part of the 
material for confirmatory tests. His success will depend upon a 
dextrous and cleanly performance of the operations necessar}' in 
the chemical analysis. 

Procedure .—Spread out the substance on a sheet of glazed 
paper, and observe whether it is an alloy or a compound; hetero¬ 
geneous or homogeneous. If the substance is in a powdered form, 

211 




212 


QUALITATIVE ANALYSIS 


examine it under a pocket lens and observe the color and form 
of the characteristic particles. Is the compound efflorescent or 
deliquescent upon standing exposed to the air? Has it an odor? 
The constituents of a mixture can often be recognized by the 
physical examination. 

The color of substances may give a clue to its composi¬ 
tion. 

Many of the oxides of metals are black; cobalt salts are gen¬ 
erally of a reddish hue when moist, and blue in the desiccated 
form: manganese salts are mostly pink; mercury, reddish yellow; 
nickel, green; copper, green and blue; chromium, green, yellow, 
red, and violet; gold, yellow. The halogens, combined with the 
alkaline earths and the alkalies, are white; chromates color 
solutions yellow, permanganates, dark red color. Regarding 
the color of the elements, many of the elements appear gray in 
powdered form, and in lumps possess a silver-white lustre when 
freshly cut. The halogens vary in color: fluorine, greenish yel¬ 
low; chlorine, yellow; bromine, dark red; iodine, purplish black. 
Silicon appears in its pure form as a black powder; boron, shining 
greenish black crystals; arsenic, black; caesium, gold, and copper 
have a yellow metallic lustre, deepening into a reddish yellow 
in the order named. Sulphur and phosphorus are translucent 
pale-yellow substances. A very large number of compounds exist 
that appear white in the powdered form; a physical examination 
of these offers but little clew to an amateur. 

Preliminary Chemical Examination. Dry Tests. 

Solid substances may be divided into two classes: 

(а) Metals or alloys. 

(б) Compounds or substances containing metals and non- 
metals, or acid radicals. 

(a) The first generally possess metallic lustre when freshly cut; 
they are malleable; a few are brittle. They all possess high 
specific gravity. 


SYSTEMATIC ANALYSIS OF A SUBSTANCE 


213 


(b) The second class usually lack metallic lustre and are more 
or less brittle and can be easily reduced to a powder. In solution 

they ionize. 

The preliminary tests will be taken up in the following order: 

A. Combustion Tube Test. 

B. Reduction or Charcoal Test. 

C . Flame Test, including spectra of the flame. 

D. Borax Bead Test. 

E. Sulphuric Acid Test. 

The first four apply to metals and the last to acids. 


A. Combustion Tube Tests 


Results of Tests 

The substance chars 

The substance swells 

The substance melts and water is evolved. 

Inferences 
O rganic matter. 

Borates,alums, Hg(CNS) 2 . 
Alkali salts, oxides, water 
of crystallization. 

The substance changes color . 


(a) Change of color due to oxides. 


APPEARANCE COLD 

APPEARANCE HOT 


White 

Yellow, unfused 

ZnO. 

Light yellow 

Yellowish brown, unfused 

Sn0 2 . 

Yellow 

Yellowish red, fuses 

PbO. 

Pale yellow 

Orange, fuses 

BLO 3 . 

Yellow 

Dark orange, fuses in high heat 

PbCr0 4 . 

Brownish red 

Dark red to brown, unfused 

Fe 2 0 3 . 

Red 

Black, fuses yellow 

Pb 3 0 4 . 

Red 

Black, globules of Hg sublimes 

HgO. 


on heating 


(b) Change of color due to dehydration. 


HYDRATED SALT 

DEHYDRATED SALT 


Green or blue 

. White or pale green 

Copper salts. 

Green 

Gray or yellowish 

Nickel or iron salts. 

Pink 

Blue or violet 

Cobalt salts. 















214 QUALITATIVE ANALYSIS 


A. Combustion Tube Tests— Continued 


(c) Change of color due to decomposition. 

ORIGINAL SUBSTANCE RESIDUE 

Colorless Red 

Colorless Yellow 

White Yellow 

Green Black 

Green Red 

Light green Black 

Blue Black 

Hg(N0 3 ) 2 

or HgN0 3 , HgO. 
Pb(N0 3 ) 2 , PbO. 

Pb(C0 3 ) 2 , PbO. 

Ni(N0 3 ) 2 , Ni 2 0 3 . 

FeS0 4 , Fe 2 0 3 . 

CuC0 3 , CuO. 

Cu(N 0 3 ) 2 , CuO. 

The substance evolves gas. 

(a) Gas is colored, and may have an odor. 

Brownish red, stifling odor 


' Oxides of nitrogen due 
to nitrates on nitrites. 

Chromyl chloride due to 
chromates and chlo¬ 
rine. 

. Bromine compounds. 

Greenish yellow, suffocating 

Chlorine from Au, Pt, Cu. 

Violet, acrid odor 

Iodine compounds. 

White fumes 

Steam. Water of crystal¬ 
lization, S0 3 , sulphates 
HC1 from chlorides. 

(b) Gas is colorless, odorless and may burn. 



Kindles a glowing chip of wood 

Oxygen from oxides, per¬ 
oxides, nitrates, chro¬ 
mates, chlorates, etc. 

Kindles a glowing chip of wood and evolves 
steam 

Nitrous oxidefrom 

nh 4 no 3 . 

Burns with a blue flame 

CO from organic com¬ 
pounds, oxalates, etc. 

Does not burn, makes a drop of limewater on 
a glass rod turbid 

CO 2 from carbonates. 













SYSTEMATIC ANALYSIS OF A SUBSTANCE 


215 


A. Combustion Tube Tests —Continued 


(c) Gas colorless, and has an odor. 

Odor of ammonia, turns red litmus blue 

Odor of burning sulphur 

(d) Poisonous gases with odor and will burn. 
Burns with purple flame, odor of peach blos¬ 
soms or bitter almonds 

Burns with blue flame, odor of rotten eggs, 
blackens lead acetate 

Burns with green flame, odor of rotten fish 
Burns with lilac flame, odor of garlic 

NH 3 from salts or organic 
matter. 

SO 2 from thiosulphates, 
sulphites, sulphates, 

sulphides. 

C 2 N 2 from cyanides of 
heavy metals. 

H 2 S from sulphides. 

PH 3 from hypophosphates. 

AsH 3 from certain arsenic 
compounds. 

The substance gives a sublimate • 

White sublimate. 


Soluble in water 

NH 4 CI, HgCl 2 , HgBr 2 . 

Insoluble in water 

HgCl, HgBr. 

Needle-shaped crystals 

Sb 2 0 3 . 

Octahedral crystals 

As 2 0 3 . 

Organic compounds 

Oxalic acid, benzoic acid. 

Black sublimate. 


From metals, or by reduction 

As, Sb. 

Violet vapors (brown in alcohol) 

Iodine. 

Gray mirror of glistening globules 

Mercury. 

Becomes red on rubbing 

HgS. 

Reddish brown sublimate. 


Brownish drops, yellow on cooling 

Sulphur. 

Brownish red, yellow on cooling 

As 2 S 3 . 

Dark red, orange on cooling 

Sb 2 S 3 . 

Yellow, turns red when rubbed 

Hgl*. 














216 


QUALITATIVE ANALYSIS 


B. Blowpipe Tests on Charcoal 

Heat a small portion of the material on charcoal in the reducing flame, 
using a blowpipe. Scoop out a round hole in the charcoal, place a little of the 
substance in the cavity, and direct the inner flame of the blowpipe against 


it at an angle of thirty degrees. 


Result of Test 

Inference 

Melts and runs into the charcoal 

Alkalies, K, Na, etc. 

An alkaline residue on charcoal 

Ca, Sr, Ba, Mg. 

A residue which, when moistened with a drop of 
Co(N 0 3 )3 and heated in 0. F., produces a color 

which is blue 

Aluminum, silicon. 

Produces a color which is green 

Zinc, tin, antimony. 

Produces a color which is red 

Barium. 

Produces a color which is pink, or rose-red 

Manganese. 

Deflagrates 

Nitrates, chlorates. 

Leaves an incrustation which is white near flame 

Antimony. 

White, garlic odor 

Arsenic. 

Dark red 

Silver. 

Red to orange 

Cadmium. 

Lemon yellow (hot), light yellow (cold) 

Lead. 

Orange yellow (hot), light yellow (cold) 

Bismuth. 

Yellow (hot), white (cold) 

Zinc or tin, latter non¬ 
volatile. 

Blowpipe Tests.—Substance fused with Na 2 C0 3 on Charcoal. Place a 

small amount of the substance on charcoal with a little sodium carbonate and 

fuse, using reducing flame. 

Result of Test 

Inference 

Metallic globules, without incrustation 


Yellow flakes 

Gold. 

Red flakes 

Copper. 

White globule, moderately soft 

Silver. 

Metallic globules, with incrustation 


White, moderately soft beads 

Lead or tin (volatilized 
lead leaves yellow coat). 

White, brittle beads 

Bismuth or antimony (yel¬ 
lowish). 

Yellow in 0. F. 

Chromium. 

Green in 0. F. 

Manganese. 

A substance (in R.F.) which, when moistened and 
placed on a silver coin, leaves a brown or black 


stain 

Sulphur compound* 











SYSTEMATIC ANALYSIS OF A SUBSTANCE 


217 


B. Blowpipe Tests on Charcoal —Continued 


Test 

Inference 

Dark gray magnetic powder, which, when moistened 
on a filter paper with a drop of dil. HC1 and HN0 3 , 
and gently dried over a flame, leaves a stain which 
is faint pink, turning blue 

Cobalt. 

Green stain, turning yellow 

Nickel. 

A stain turned blue by K 4 Fe(CN)6 

Iron. 


In place of using charcoal the above tests may be made with a splinter of 
wood covered with a coating of fused Na 2 C0 3 . The test is made by dipping 
the heated splinter into a mixture of the powdered substance with fused sodium 
carbonate and plunging for a moment in the reducing flame. Examine the 
material on the splinter, scrape off on a piece of glazed paper and examine. 

Blowpipe Tests.—Substance moistened with cobalt nitrate solution and 
ignited. 


Color of Residue or Incrustation 

Inference 

Brick red 

BaO. 

Pink. 

MgO. 

Gray 

SrO, CaO. 

Yellowish green 

ZnO. 

Dark muddy green 

Sb 2 0 5 . 

Bluish green 

SnO. 

Blue 

A1 2 0 3 , Si0 2 . 


C. Flame Test 


Moisten a clean platinum wire in strong HC1, dip into the powdered sub- 
I stance and insert into a Bunsen flame. If sodium is present examine through 
[ a blue glass. (Test the cobalt glass to see if it is effective in cutting out the 
yellow sodium light by examining a sodium flame through it.) 


i Flame Color. 

Carmine red 
1 Dull red 
|! Crimson 
I Golden yellow 
Greenish yellow 
Green 
Blue 
Violet 


Color through Blue Glass. 
Purple 
Olive green 
Purple 
Absorbed 
Bluish green 


Violet red 


Element. 

Lithium 

Calcium 

Strontium 

Sodium 

Barium, molybdenum 

Cu,-P0 4 ,-B 2 0 3 

Cu, Bi, Pb, Cd, Zn, Sb, As 

Potassium 









218 


QUALITATIVE ANALYSIS 


The platinum wire should be cleaned before making the test. This can be 
accomplished by dipping it into cone. HC1 and holding it in the Bunsen, or 
better, a flame of a blast lamp, until the flame is no longer colored. Repeat¬ 
edly dipping into the HC1 may be necessary. 

Examine the flame through a spectroscope, if available, and compare the 
spectra with a spectra chart. Mere traces of the alkali and alkaline earth 
metals can be detected in this way by their characteristic spectral lines. 


D. Behavior of Substances fused with Microcosmic Salt and Borax Beads 

A clear bead is formed by fusing the flux on a loop of platinum wire. Dip the bead in the finely powdered substance 
to be examined y and heat again—first in the oxidizing flame ; second in the reducing or inner flame. Metallic salts 
are mostly changed to oxides. In the Table— h. signifies hot; c., cold; sups., supersaturated with oxide; s. s., 
strongly saturated; h. c., hot and cold. 


SYSTEMATIC ANALYSIS OF A SUBSTANCE 219 


With. Sodium Tetraborate (Borax). 

In inner or reducing Flame. 

Si, Al, Sn ( s. s. opaque). 

Alkaline earths and earths. 

h. c.\ Mn, Ce. 

h.: Cu. 

h.: Ti, Mo. 

r.: Cu (sups, opaque). 

$3 

o’ 

U 

d 

* 

Fh 

d 

• C». 

r *S a 

O on 

The same as with micro¬ 

cosmic salt. 

: In outer or oxidizing Flame. 

o 

*> a 

d < .H 

§* cf H 

~ " e' 

“ .a 

, fc ft 
» bo* 5 - 

« <1 N 

p 5 

;:ft 

■§* 

© 

O 

qTmh 

ftfc 

« d 

6 

o 

g 

si 

•:fc 

t ,, 

rc; tCt 

o 

°.d 

d» 

rd ti 

d 

o 

.d 

« 

ft 

5 5 

d « 


With Microcosmic Salt, Sodium Ammonium 
Hydrogen Phosphate. 

In inner or reducing Flame. J 

d 

B. 

^ a- 

0) 

13 

W 

P „ 

3 ai ^4, ri 

R Of 

H 

0) 

Fnfc 

.c; ti 

d 

ft 

,4 

? 

H 

55 

ti rfS 

H 

6 

o 

u . 

rfi ti 

d 

.» 

ti « 

£ 

d 

n 

8 

w 

£ 

bo 

< 

In outer or oxidizing Flame. 

Si (swims undissolved): 

Al, Mg, Ca, Sr, Ba, Sn 
($. s., opaque ). 

Ti, Zn, Cd, Pb, Bi, Sb 

( not sat.). 

© 

<u 

ft 

09 H > 

rfi d 

6 

u 

o 

£ 

,a> 

ft 

d 

d 

d 

s 

d 

«c 

c" 

« d 

h.: Cu, Mo; Fe with Co or 
Cu. 
c.: Cr. 


Color of the 

d 
o> 

n 

Colorless. 

Yellow 

or 

Brownish. 

*d 

QJ 

w 

Violet 

or 

Amethyst. 

© 

d 

5 

c 

V, 

© 

t- 

e 

Gray and 
Opaque. 
















































220 


QUALITATIVE ANALYSIS 


E. Sulphuric Acid Tests. The Acids 

Sulphuric acid volatilizes a number of acids, some of which can be posi¬ 
tively identified by their odor or color. 

Method. —Place a small portion of the solid in a test tube, add a few drops 
of cone. H 2 S0 4 , and observe results; now heat cautiously, but do not boil. 
Note the color of the gases evolved, and by holding the test tube at a slight 
distance and fanning the fumes with the hand toward the nose, gradually 
bringing the test tube nearer, note the odor of the gases. 


Result of H 2 S0 4 Test 

Inference 

Colorless gases with or without odor generally 
effervescent. 


Material turns black, odor of burnt sugar 

C 2 H 4 O 6 , tartrates. 

Odor of vinegar or acetic acid 

No odor, makes turbid a drop of limewater on a 

C 2 H 3 O 2 , acetates. 

glass rod 

CO 2 , carbonate or oxalate. 

No odor, burns with a blue flame 

No odor, with addition of alcohol burns with 

CO, oxalate or ferrocyanide. 

green flame 

B 2 0 3 , borate. 

Odor of rotten eggs, blue flame, blackens lead 

H 2 S, sulphide or sulphite 

acetate paper 

Odor of burning sulphur, blackens paper mois¬ 

-{-reducing agent. 

tened with HgN0 3 

SO 2 , sulphite. 

Same as above—free sulphur pptd. 

SO 2 , from S 2 0 3 , thiosulphate 

Corrodes the test tube 

HF, fluorides. 

Odor of HC1, white fumes with NH 4 OH on rod 
Colorless, having an odor of bitter almonds or 

HC1, chlorides. 

peach blossoms, extremely poisonous vapor 
Colored gases with odor. 

C 2 N 2 , cyanide, ferrocyanide. 

Yellowish, pungent odor 

Cl, hypochlorite, chlorate+ 
reducing agent, chloride+ 
oxidizer. 

Yellowish green, suffocating, explosive 

C10 2 , chlorate. 

Brownish red, stifling odor 

HBr, Br, bromides. 

Brown or deep red vapor, suffocating 

Violet vapor, acrid odor, separation of black 

NO 2 from nitrites or nitrates 

powder 

Precipitate formed. 

I, iodides. 

White precipitate, flocculent 

H 2 Si0 3 , silicates. 






SYSTEMATIC ANALYSIS OF A SUBSTANCE 


221 


PRELIMINARY EXAMINATION OF A LIQUID 

If the material is a liquid test this with litmus paper; if neutral, 
evaporate a few drops on a platinum foil over the flame, or on a 
watch glass (on a water bath) if volatile products are suspected. 
If there is no residue left, the substance is pure water. 

If the solution is acid, either free acid is present or an acid 
salt, such as sodium hydrogen sulphate, or alum. 

If the solution is alkaline, the substance may contain free 
alkali or the alkali salt of a weak acid. 

ANALYSIS OF THE METALS 

The preliminary examination of the solid often affords positive 
indications of its composition; for a more extended examination, 
however, it is necessary to get the substance into solution and to 
; test for its components by liquid reagents. 

Before this can be done certain interfering substances must 
be removed. We learned in our study of the metals of the Ammo¬ 
nium Sulphide Group that organic matter interfered in precipita¬ 
tion of certain metals. Oxalic and phosphoric acids caused 
. precipitation of metals of succeeding groups. Provision must be 
made against such interference by removal of the substances in 
question. 

Organic Matter.—The charring of the substance by heating 
in the preliminary test and the odor have indicated the presence 
of organic matter. This may be removed by combustion at 
red or white heat, but this would cause volatilization of certain 
substances such as ammonia, mercury, arsenous, and antimonous 
compounds. An effective procedure is by oxidation of organic 
matter either by heating it with strong HC1 and adding KClOs 
, crystals or by adding strong HNO 3 followed by concentrated 
H2SO4 and heating to fumes, preferably in a round-bottom flask. 
The heating being continued until the solution changed from a 





222 


QUALITATIVE ANALYSIS 


black tarry mass to a straw-colored solution. Should the hydro¬ 
chloric acid procedure be employed the metals would be in form 
of chlorides while the last method would form sulphates. 

Oxalic Acid—This is destroyed by the procedure used for 
removal of organic matter. 

Phosphoric Acid.—Reference is made to the notes on the 
metals of the Ammonium Sulphide Group for the detection of 
phosphoric acid and the procedure and for its removal, page 115. 

Preparation of the Solution for Detection of the Metals 

I. SUBSTANCES SOLUBLE IN WATER. 

Salts and Oxides .—Water as a Solvent .—To about one gram of the well- 
mixed substance, pulverized in a mortar (test small portion for explosives, etc. 
KCIO 3 ) and placed in a large test tube, add about 10-20 cc. of distilled water; 
boil for 10 minutes; allow to settle if any residue remains. Test with litmus 
paper. If solution is neutral or acid, filter. Add more water to any residue 
that may remain; boil and filter, combining filtrates. If considerable residue 
remains evaporate a portion of the extract to dryness and observe whether a 
residue remains. The material in solution is examined by the standard scheme 
for analysis. Water insoluble material is treated as directed below. 

II. SUBSTANCES INSOLUBLE IN WA TER AND SOLUBLE IN ACIDS 

Should the substance not dissolve in water it must be treated by the Acid 
Solvents. If the dry tests have indicated Ag or Pb, or if the litmus test indi¬ 
cated an alkaline reaction, use the HN0 3 Method B. Otherwise dissolve the 
residue by the HC1 Method A. 

A. HC1 Method of Solution.—Pour about 10 cc. HC1 (1.12) over the residue 
and warm. If solution is not complete, add 5 cc. of HC1 (1.20), and warm as 
long as any substance appears to dissolve, renewing the acid lost by evapora¬ 
tion. If the residue still remains, dilute with 5-10 cc. of water and filter by 
decantation. Pour 5 cc. aqua regia over the residue, and heat for 5-10 minutes. 
If a residue still remains, the solution must be filtered and the filtrate evap¬ 
orated, otherwise evaporate the clear solution almost to dryness; add 2-3 cc. 
more HC1 (1.20) and reevaporate to dryness over flame to expel the HN0 3 . 
Dissolve the baked residue in HC1 ( 1 . 12 ) and add H 2 0; combine with the HC1 
solution. Analyze this solution for the bases, beginning with the H 2 S Group. 

B. HNOs Method of Solution.—To the residue, or if the solution is alka¬ 
line, add without filtering 5-10 cc. of HNOs ( 1 . 20 ) and heat to boiling, and 







SYSTEMATIC ANALYSIS OF A SUBSTANCE 


223 


evaporate just to dryness in a casserole by keeping the dish in motion over a 
free flame. Dehydrate the residue, loosen from the dish, and to the powder 
add 5-10 cc. HN0 3 (1.20); warm on hot plate or steam bath 5-10 minutes; 
dilute with 10-15 cc. of water; heat to boiling; filter and wash residue, adding 
the washings to the filtrate. 

C. Aqua Regia Treatment of Substances Insoluble in HC1 or HN0 3 .— 

To the residue remaining undissolved by HN0 3 add 5-10 cc. HC1 (1.20) 
and heat, adding more acid to replace evaporation. If residue still remains, 
add to the mixture one-third of its volume of HN0 3 (1.20), heat gently as 
! long as an action continues, replacing the evaporated acids by more aqua regia. 
To the solution or the mixture, if a residue still remains, add the filtrate from 
| the HC1 Group above mentioned, evaporate nearly to dryness, and expel the 
j HN0 3 by the method described in the “ HC1 Method of Solution,” by repeated 
evaporation with HC1. 

III. RESIDUE IN SOLUBLE IN ACIDS. ____ 

i There are but few substances that do not go into solution under the treat- 
| ment above prescribed. The following are the principal insoluble products 
that are apt to be left in this residue: 

(a) C, S (liberated by HN0 3 from sulphides). 

( b ) AgCl, (AgBr, Agl), PbS0 4 , PbCl 2 . 

(c) BaSCL, SrS0 4 , CaS0 4 , Si0 2 , Cr 2 0 3 , and silicates. 

(d) A1 2 0 3 , Fe 2 0 3 , Sn0 2 , Sb 2 0 3 . 

(e) CaF 2 , cyanides, ferrocyanides of the heavy metals. 

j Substances under (a), (6), and (e) have been indicated by the dry tests. 

(a) If sulphur or carbon is present, remo ve by ignition in a crucible. 

Residue ( b ), (c), {d), (e).—The halogen salts of S and C volatilize as 

! silver have been indicated in the dry tests Ag(Cl, oxides. __ 

. etc., reduced to Ag by charcoal test) and the halides 

i indicated by the H 2 S0 4 test. . 

The chloride and bromide are soluble in an excess of NH 4 OH, the iodide in 

a strong solution of KI. All are soluble in KCN. 

Two general procedures are used for getting refractory substances into 
j solution, hydrofluoric aci d treatment and the fusion method. _ 

A. Hydrofluoric Acid Method for Refractory Material Insoluble in 
| Aqua Regia.— Transfer the residue from the acid solutions to a platinum cruci¬ 
ble. Add 2 cc. H 2 S0 4 (1.84), heat with moving flame until white fumes are 


















224 


QUALITATIVE ANALYSIS 


given off, then cool, add carefully, using loop of a platinum wire, 5-6 drops 
of HF (40 per cent). Warm over a steam bath. (Bubbles are due to SiF 4 .) 
Add 5 cc. more of HF (40 per cent), and cover crucible with Pt cover and 
digest on steam or water bath 10-15 minutes unless the residue dissolves 
more quickly. Remove the cover and evaporate, using moving flame until 
white sulphuric acid fumes evolve. Cool and pour the contents of the 
crucible into 10 cc. of water, and add to this the rinsing. Boil the mixture, 
cool, and filter. Wash the residue first with H 2 S0 4 and then with water. 
Reject the washings. 


Residue.—PbS0 4 , BaS0 4 , SrS0 4 , 
CaS0 4 , Bi 2 (S0 4 ) 3 , Cr 2 (S0 4 ) 3 , Sb 2 0 3 , 
Sn0 2 , A1 2 O s , Fe0,Cr 2 0 3 , and insolu¬ 
ble silicates. 

Transfer to casserole and add 15-20 

Filtrate.—Add HC1 drop by drop as 
long as a precipitate forms. 

Precipitate.— 

AgCl, white, sol¬ 
uble in NH 4 OH. 

Test for all metals 
except Pb, Ba, Sr, 
and Ag. 

cc. oi a saturaiea soiuuoii oi iNa 2 v^w 3 , 

boil gently 5-10 minutes, filter, and wash thoroughly. 

Residue.—Carbonates and sulphates 
Sr, Bi, Pb, Ba, and native oxides and si 
Heat with 5 cc. HC1 (1.12) and 10 cc. I 

i of Ca, Filtrate.—Contains W. 

licates. 

J 2 0. Filter and wash. 

Residue.—Sulphates of Cr, Ba, Mo, 
and oxides of Sb, Sn, Al, Cr, etc., and 
the silicates. Fuse the residue with 

Solution.—Dilute to 40 cc. and test 
for Pb, Bi, Sb, Ca, Sr, Ba, which may 
be here as chlorides. 

JNa 2 UU 3 +-nJNIU 3 1U : l, according to 

directions given in first method. Dissolve by adding HC1 (1.12) until strongly 
acid; evaporate to dryness, and heat over flame, cool, and add 4 cc. HC1 (1.12 
and 20 cc. H 2 0; boil and filter. 

Residue.—Si0 2 , BaS0 4 , A1 2 0 3 , Sn0 2 . 
Si0 2 and BaS0 4 by HF+H 2 S0 4 proc 
verize any remaining residue, and fuse i 
or silver crucible with solid KOH foi 
water; neutralize with HC1, extract anj 
solution, which, <jf course, will contai] 

Remove Filtrate.—Test for all 

ess. Pul- elements except the alkalies. 

n a nickel 

• 10-20 minutes, cool and extract with 
7 residue with 5 cc. HC1(1.12). Analyze 
n Ag or Ni from the crucible. 


B. The Fusion Method of Refractory Material Insoluble in Aqua Regia.— 

Two kinds of fluxes are used: (1) Alkaline Flux, Na 2 CC >3 (together with 
either an oxidizing agent, KN0 3 , or a reducing agent, KCN). (2) Acid Flux , 
KHS0 4 . 


















SYSTEMATIC ANALYSIS OF A SUBSTANCE 


225 


The fusion is best carried on in a platinum dish, provided no substance 
deleterious to platinum is present; otherwise in a quartz crucible. (In the 
latter case Si, Ca, and A1 may be introduced from the crucible; hence tests 
for these are not reliable.) 

Method .—-Add to the pulverized substance five times its bulk of Na 2 C0 3 (or 
a mixture of 4 parts of Na 2 C0 3 -|-l part of KNO). Heat to high temperature 
over a powerful flame until the mass has reached a state of quiet fusion. Cool 
and place the crucible on its side in a small beaker, half cover with water and 
boil, adding more water if necessary. Wash the residue with boiling water 
until free of alkalies. (If sulphates are not present, treat the disintegrated 
substance directly with dilute HC1, and test for silica as stated under filtrate.) 
Filter. 


Residue.—BaC0 3 , SrC0 3 , CaC0 3 , 
and (a), (e). See III, page 223. 

Dissolve in a small amount of HC1 
(1.12) and heat to about 100°. Add 
more water and HC1, and filter. 

Filtrate.—Na 2 S0 4 , Na 2 Si0 3 , etc. 
Test for S0 4 by BaCl 2 test. 

For silicates, evaporate to dryness 
with HC1. See subject in Acid 
Analysis. Test for Al, Zn, Cr, As, 
and P0 4 . 




Residue (d), (e ).—Fuse the residue 
with KHS0 4 at a moderate temper¬ 
ature. (High temperature will form 

Filtrate.—Ba,Sr, Ca,Cl 2 ,etc. Add to 
solution to be tested for H 2 S, (NH 4 ) 2 S 
and (NH 4 ) 2 C0 3 Groups. 

msqiuDie oasic suipnate.; v_,ooi alter 

10-15 minutes and dissolve in water. 

Residue.—Sn0 2 . This oxide may be 

Filtrate.—Al +++ , Cr+++, Fe +++ 


dissolved by fusing with S and Na 2 C0 3 . S0 4 . Test along with above 

Dissolve the Na 2 SnS 3 in water and filter, solutions. 


with 

yellow 


HC1. 

ppt., 


^To disintegrate the Members (e).—Add 
cone. H 2 S0 4 in a platinum crucible and 
; heat. HF and HCN will escape as gases. 

A hang drop (water in Pt loop) held in the 
i fumes will absorb silicon tetrafluoride, and become cloudy. See page 188. 


Filtrate.—Acidify 
If Sb is present, a 
SnS 2 , will form. 


















226 


QUALITATIVE ANALYSIS 




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SYSTEMATIC ANALYSIS OF A SUBSTANCE 


227 


s a a°a 

p 0 
















QUALITATIVE ANALYSIS 


228 


Aqua Regia Method 


Dissolve the alloy in a mixture of IIC 1 and HN 0 3 (3 : 1 ) warming gently, 
dilute with water and again heat. Cool and filter. 

Precipitate.—PbCl 2 
Test for lead by usual 
procedure. 

Filtrate.—If lead has been shown to be present, 
remove as a sulphate by taking to fumes with addition 
of H2SO4, cooling, diluting and filtering. 

Precipitate.—PbSO 4 
reject. 

Filtrate.—This may contain members of the H2S 
group, A and B, and members of following groups. 
The elements are separated according to the pro¬ 
tables of separations of the metals in Part II. 

cedures outlined in the 


Individual Tests 

Frequently it is desired to ascertain the presence of a constituent in an 
alloy without attempting to separate the other elements present. Rapid 
tests may be made for many of the metals by more direct methods than 
those outlined in the tables of separations. These tests may be found in the 
descriptive portions of Part II under “ Detection ” for the more common 
metals and in Part VI for the less common elements. 


Among the more familiar alloys the following are of interest. The princi¬ 
pal elements are given in heavy type under A. The less commonly occurring 
elements are given in lighter type under B. 


Name of Alloy 

Bearing metals 

Brass 

Bronze 

Britannia metal 
German silver 
Solder 
Type metal 


Composition 


a 

Copper, lead, tin 
Copper, zinc 
Copper, tin 

Antimony, tin 
Copper, nickel, zinc 
Lead, tin 

Antimony, lead, tin 


B 

arsenic, antimony, zinc, 
arsenic, lead, tin. 
arsenic, antimony, lead 
phosphorus, zinc, 
arsenic, copper, lead, 
arsenic, lead. 

arsenic, antimony, copper, 
arsenic, copper, cobalt, nic¬ 
kel, zinc. 


Special alloys.—Alloys containing the less common elements. 














SYSTEMATIC ANALYSIS OF A SUBSTANCE 


229 


ANALYSIS OF THE METALS 

As a general rule the number of the bases to be looked for is not large, 
and all the groups are not represented. Time is frequently saved by making 
a preliminary test for the groups present on a small portion of the sample, 
so that unnecessary addition of group reagents may be avoided in the proced¬ 
ures for complete separation of the common elements. The general scheme 
of analysis is now followed in the usual order, avoiding the groups found to be 
absent by the preliminary examination. 

The material is dissolved according to the procedures outlined 
on pages 223 to 228. 

SEPARATION' OF THE GROUPS 

To the Solution add HC1. 

Precipitate: AgCl, HgCl, PbCl 2 . 

Filtrate: Pass in H 2 S. 

Precipitate: CdS, CuS, Bi 2 S 3 , HgS, PbS, AS 2 S 3 , Sb 2 S 3 , SnS. 

Filtrate: Boil, add NH 4 OH and (NH 4 ) 2 S. 

Precipitate: Al(OH) 3 , Cr(OH) 3 , FeS, CoS, MnS, NiS, ZnS . 

Filtrate: Boil, add (NH 4 ) 2 C0 3 . 

Precipitate: BaC0 3 , CaC0 3 , SrC0 3 . 


Filtrate contains Na, K, Mg. 

The precipitates, collected on filter papers, are thoroughly 
washed with distilled water and then dissolved and analyzed 
according to the procedures outlined in Part II. The following 
table, pages 230 and 231, give a summary of the procedures. 













Solvents in order of preference—H.O.dil. HCl.conc. HC1, dil. HN0 3 , cone. HN0 3 , aq. rcg. Refractory Substances— H,SO«+HF, fusions with 
Na 2 C0 3 , KHS0 4 , NaOH or KOH. Anal)-sis- Neutral or slightly acid solutions of the salts of —- 


230 


Pb 

Hg' 

Ag 

As'" 

As v 

Sb v 

Sb'" 

Sn ,r 

Sn" 

Au’" 

p t iv 

Mo vl 


Hg" 

Pb 

Bi 

Cu' 

Cu" 

Cd 


A1 


Cr'" 

Cr vl 


Fe' 

Fe' 


Co 

Ni 


Zn 

Ba 


Sr 

Ca 

Mg 


K 

Na 

NH, 


QUALITATIVE ANALYSIS 


Mn" 

Mn v “ 


Q. 00 o 

o 


g so 
o. ~ 


PbClj (w) 

*3 

O ^ 

HgCl(w) 


AgCl(w) 





TABLE FOR REVIEW OF THE SEPARAT 
PbCI 2 Tests (a) +H 2 S0 4 = PbS0 4 white. (ft) +H,S = PbS l 


HgCl 

AgCl 


Add NH,OH 


Residue-NH : HgCl+Hg black. 


Solution—(NH 3 );(AgCl)j} acidify wit 


As.S 3 (y) 
AsjSj (v) 
Sb^S. (o) 
Sb 2 S 3 (o) 
SnSj (y) 
SnS (hr) 
Au 2 S 3 (br) 


2 PtS, (bk) 

* | MoS 3 (br) 


2 ( 


HgS (bk) 
PbS (bk) 
Bi 2 S 3 (br) 
Cu.S (bk) 
CuS (bk) 
CdS (y) 


- sc 

3 -C 


co O 


i3 

o -o 


o x 


“ -o 
o 

-O _C 

E 


E 3 


O 
X 
X 

TJ -73 


*2 c 


w •§ 

ws 


u — 


c§ 


(NH,) 1 As 2 S i 

(NH.hAsS, 

(NH 4 ) 3 SbS 4 


a (NH 4 ) 2 SnS 3 

o <* 

a; 

Solution. 

Solution. 

(NH 4 ) 2 MoS 4 


« 2 
■c ° 
-2 .9 

•S H 


i- o 


As 2 S 3 
A S ; S j 

Sb 2 Sj 


SnSj 


Au 2 S 3 

PtS, 

MoS 3 


a a 

«2 

>o 

o W 


tn * 


Q_. 


H 3 As0 4 


SbCL 


SnCl 4 


AuCl 3 

PtCl 4 

MoCU 


~c O 


HgS 
. PbS 

| Bi,S, 

o Cu 2 S 

c2 

CuS 

CdS 


HgS 


Id 

Pb(N0 3 )j 

t n • 

cO 

ZK 

Bi(N0 3 ) 3 

Sk 


Cu(N0 3 ) 2 

o2 

Q -0 

Cd(N0 3 )i 

=Si2 

< c 


Dissolve in nitrohydrocl 
*PbS0 4 
^ Bi(N0 3 ) 
g Cu(N0 3 


eg Cd(NO, 


c . 
o o. 
►3 3 


2 Al(OH) 3 (w) 

CJ 

|cr(OH) a (g) 

o ■ 

£ Fe(OH) 3 (r) 


"O 

<u 


a 


• Cr(OH)j ] Fuse on platinu 
2 KN0 3 and Na 2 CO 

w Fe(OH)j | Extract with w: 


5 a 


13 

H % 

* o 
X u 


o 

CU) 

s 

13 


CoS (bk) 

| NiS (bk) 
5. 

| MnS (pk) 

Cl, 

ZnS (w) 


~X 


'/. — 

Q 


. CoS 


NiS 

MnClj 


ZnCI 2 


. 

N .C O 

3 r2 

PQ -u o 
X _4) 13 


<3 — 
<N ”3 


9 'S 


^ S 

S grg 

2 5 


3 CL 


-"5 m 2 


oo 


BaC0 3 

SrCO } 

CaCOj 


W 

o 

x 

X 


r-a a; 


13 


O 2 

. £3S 3 o: 

g PC C C.-73*D 4 

I nm 

^ a oZ: 
PL. «) W - 


Abbreviations: (w) = white; (y)=yellow; (o)='orange; (br)=brown; (bk) ■ 


































































SYSTEMATIC ANALYSIS OF A SUBSTANCE 


231 


HE METALS. ANALYSIS OF THE SOLUTION. 
K 2 Cr0 4 = PbCrO« yellow, (d) +KI = Pbl, yellow. 


Cl white. 


AsH , gas 


SbHj gas+Sb' 


^ o_; c-c 
3.S * ” e3 
"§ 2n'-o •- 
tig o 2 i2 

^ - 2 

_c c a. 

♦-<»<. C (A 


HjAsOj j Remove AgNOj with CaCl„ and add HjS{AsjS 3 Lemon yellow. 
Giitzeit Test—AsH 3 colors HgCl 2 paper a deep maroon. 

, See method on page 40. 

SbAg 3 } Dissolve in hot HC1, dilute, filter and add H 2 S[SbjS 3 Orange. 


Sn If j 
£ cj 


SnCl, 

Sb 


&£ ! Au 


.2- *• I 

ers 


l Pt 


Test with HgCl 2 . { HgCl, White; or Hg Gray. 


S4s f SbCl s 
AuC1 3 

°li l Ptci 4 


i=aO 


SbCli reject or test in Marsh apparatus. 

o--i , — . {. Au , ci j- NHjCI Evaporate and 

D, of NH,C1 aod digest ignite to Au , Yellow. 

• I Pt J wltrt alcohol. \ (NH 4 ) 2 PtCl 6 Ignite to Pt°, Gray. 

IJlue togrecn-hrown \ Evaporate to dryness with excess of HN0 3 . Dissolve res. in NR,OH and add to an 
or black solution. f excess of HC1. Test this sol. with Na 2 PHO<Ammonium phosphomolybdate, Yellow. 


:i and precipitate with (NH«)jCOj{ Al(OH) s White, gelatinous. 

j 0 j (K 2 CrOi and j Acidify with HC 2 H 3 0 2 and add Pb(C 2 H 3 0.) 2 [ PbCr0 4 Lemon-yellow. 

\ Na 2 Cr0 4 ^ Dissolve in HC1 and add KCNS | Fe(CNS) 3 Blood red. Test original solution (acid) 
Res. Fe(OH), j w ith KCNS for Fe'" and with K 3 Fe(CN) 6 for Fe"{ Fe 3 (Fe(CN),] 2 Blue 


1 ^cst with (a) SnCl 2 = White HgCl or Gray to Black H, 
jrrpation of Pbl 2 or PbCr0 4 . See Pb above. 

Bi(OH) 3 Add hot K 2 Sn0 2 pouring over ppt. on filter.', Bi Black. 
Cu(OH) 2 .2NH,OH.2NH 4 NO} ] Deep blue solution evidence of copper. 


(i>) Au wire = Hg on wire. 


For traces add HC 2 H 3 0 2 and test with K 4 Fe(CN) 6 J CuJFe(CN) s Red-brown, 


Cd(0H),2NH,0H.2NH 4 N0 3 


Add KCN till blue color disappears, then H 2 S{ CdS 


Lemon-yellow. 


>C1 2 

CL 

n(OH) 2 


a. Test with borax bead. Blue bead. 

b. Add NaHC0 3 and H 2 0 2) Green solution. 
a. Test with borax bead. Brown bead. c. 


b. Heat with Br 


\ add KI. 


and NaOH { Ni(°H)j j Free I in CS^ 


c. Or evaporate +H 2 S0 4 and add nitroso-d-naphthoL 
Co—Red precipitate. Test with borax bead. 
Or make sol. ammoniacal and add 1% 
alcoholic sol. nitrosobetanaphthol « 
I(CH 3 ) 2 C 2 N 2 0 2 H] 2 Ni Red. 


Boil with Pb0 2 and HNOj', HMnO, , Puri>Ie. 


i 2 Zn0 2 | Add H 2 S} ZnS White. Ppt. is insoluble in dilute acetic acid. 


,Cr0 4 

C 2 H 3 0 2 ) 2 

(C 2 H 3 0 2 ) 2 

Dissolv* 

^<5 

•3 0^ 

; in HC1 

SrC0 3 

CaC0 3 

ind add H 2 S0 4 ^BaS0 
e '• 

J§ Sr(C 2 H 3 0 2 ) 2 

vi (J! 

gW Ca(C 2 H 3 0 2 ) 2 

4 White. 

$ a 1. Add CaS0 4 set aside 10 minutes | SrS0 4 White, 
.£ § Moisten SrS0 4 with HC1 and apply flame test, 
-g-g 2. Add K 2 S0 4 , boil, set aside ten minutes. 

> o Filter and add t CaCj04> White 80 i ub i e in HCL 
Qcr (Wii 4 ; 2 c 2 u 4 i 

Precipitate MgNH 4 P0 4 White. 


K—Apply flame test using cobalt glass. Violet. 

Na—After removal of Mg apply flame test, yellow, 

NH 4 —To the original solution add KOH in strong excess, warm (note odor) and test with moist litmus 
paper; pass gas into Nessler’s reagent K 2 HgL sol. { NHg 2 I, Brown 

:d; (g)=green; (pk)=pink. Ppt. = precipitate. Res. = residue. Sol. = solution 


































232 


QUALITATIVE ANALYSIS 


ANALYSIS .OF THE ACIDS 

During the systematic examination for the cations, the presence 
or absence of certain acids have been ascertained. The carbon¬ 
ates, nitrites, sulphides, sulphites, etc., are volatilized by H2SO4, 
also, when H 2 S is passed into the solution for the analysis of that 
group, a yellow-colored solution, changing to a green, indicates 
a chromate. Then, again, the presence of phosphates was ascer¬ 
tained before completing the analysis of (NLL^S Group. Fur¬ 
thermore, the presence of certain metals in a solution soluble in 
water or dilute acids will indicate the absence of certain acids. 
For example, barium and the sulphate radical cannot exist in a 
solution, nor can a halide and silver be present in a salt that readily 
dissolves in water or a dilute acid. A number of acids have been 
identified by the sulphuric acid test for acids, so that our problem 
is not as complex as one might first be led to believe. Moreover, 
the number of acids to be looked for is comparatively few; this 
is especially true of natural products such as soils, rocks, 
minerals and the like. 


General Rules for Solubilities 


Salts Soluble in Water 

Salts of Na, K, Li, NH 4 

All Nitrates and Nitrites 

All Chlorates 

All Chlorides 

All Bromides 

All Iodides 

All Sulphates 

All Acetates 

Exceptions 

Some basic nitrates insoluble 

Chlorides of Ag,Hg, Pb, Cu - , insoluble 
Bromides of Ag, Hg,Pb, Cu~, insoluble 
Iodides of Ag, Hg, Hg -- ,Pb, Cu~, 
insoluble 

Sulphates of Ba, Ca,Sr, Pb,Hg + insol. 
Basic acetates of some metals, insoluble 

Insol. in Water, Sol. in Acids 

Exceptions 

All Carbonates 

The alkali salts are soluble 

All Phosphates 

The alkali salts are soluble 

All Borates 

The alkali salts are soluble 

All Oxalates 

The alkali salts are soluble 

All Tartrates 

The alkali salts are soluble 

All Arsenates and Arsenites 

The alkali salts are soluble 







SYSTEMATIC ANALYSIS OF A SUBSTANCE 


233 


Preparation of the Solution for Acid Analysis 

Since the preparation of this solution depends largely upon the basic con¬ 
stituents present, this portion of the analytical work is taken up after the 
completion of the analysis of the cations. The chemist is now in a position 
to intelligently prepare the solution and to interpret reactions that will follow 
in the acid tests. 

A. Substance Soluble in Water or Dilute Acids. Heavy Metals Absent.— 
(Cu, Hg, Bi, Cu, Cd, Sb, As, Sn, Fe, Al, Cr, Zn, Mn, Co, Ni, etc., sp.gr. above 
5.) Dissolve in water or dilute acid and use directly for acid analysis. 

B. Substance Soluble in Water. Heavy Metals Present.—Add to the 
solution containing the substance 10-15 cc. of a saturated solution of Na 2 C0 3 
and boil for 15-20 minutes, replacing water if necessary. Add about 10 cc. 


of water, and filter. 

Precipitate the heavy metals Filt 

as carbonates. Reject. ionize 

rate.—Filtrate containing the acids as 
d sodium salts. Neutralize with acetic 
ind use for acid analysis. 

present among the heavy metals, acidify 
with acetic acid and pass in H 2 S as long 

acid a 

Note .—If arsenic or antimony are ] 
the filtrate of the insoluble carbonates 
as precipitation takes place. 

Precipitate.—Sulphides of As and 
Sb. 

Filtrate.—Expel the H 2 S by boiling 
and use for the acid analysis. 

C. Substance Insoluble in Water.—Boil a gram of the substance with 
15 cc. of a saturated solution of Na 2 C0 3 . (Add to the substance 3-4 times 
its bulk of the soda and a little water sufficient to dissolve the Na 2 C0 3 .) Boil 
10 minutes and filter; wash with small quantities of water. 

Residue.—Carbonates of the heavy 
metals. (Fusion with Na 2 C0 3 may be 
necessary in some cases.) 

Filtrate.—Sodium salts of the acids. 
Acidify with acetic acid. (Excess of 
carbonate is destroyed.) Now add 
NTT .OH in slio-ht, excess, and boil until 


excess is expelled. Use this solution for acid analysis. 


Notes .—If only heavy metals are present which can be precipitated by II 2 S, 
they may be removed by suspending the solid in water and passing in H 2 S for 
about 20 minutes. Filter and boil the filtrate to expel H 2 S, and use for analysis. 

If the solution is colored by a permanganate, it can be decolorized by boiling 
with a few crystals of oxalic acid; filter if necessary. 

Acids used to bring the substance into solution and volatile acids should 
be tested for in the original substance. 
















234 


QUALITATIVE ANALYSIS 


Preliminary Tests for Groups 

Silver Nitrate Group 

Acidify a portion of the solution for the acid analysis with dilute HNO3, and 
add AgN0 3 solution, drop by drop, as long as a precipitate forms. Filter. 


Precipitate.—Silver the salts of the group. 

Color Inference 

White C1-, CN-, CIO", SCN- 

Light yellow Br-,Fe(CN)e , I - 
Orange yellow Fe(CN ) 6 

Black S sulphides, thiosulphites 

Add NH 4 OH to the precipitate after washing 
by decantation; shake thoroughly and filter. 


Residue.—Ag salts of Br , 

Fe(CN)e-, Fe(CN ) 6 - 

CIO", SCN~, I. 

See method of analysis un¬ 
der HN0 3 Group. PartUI. 


Filtrate.—Cl , 
CN“. Add dil. 
HN0 3 and boil 
to expel—CN _ . 

Residue.— 
AgCl. 


Filtrate.—The Barium and 
Soluble Groups. Pour a few 
drops on a white porcelain 
tile, and place a drop of 
NH 4 OH by means of a glass 
rod carefully on the solution. 
A colored ring will appear. 

Color Inference 
Yellow H 3 As 0 3 or H3PO4 
Brown H 3 As0 4 
Red H 3 Cr0 4 

White H2SO3, HPO3, etc. 


Note .—A colored halide insoluble in strong NH 4 OH is an iodide of silver. 
AgCl is white and is easily soluble in NH 4 OH. AgBr is slightly soluble. 


Barium Chloride Group 


Make a portion of the neutral solution, just acid with a few drops of HC1. 
A cloudiness may be due to thiosulphates or sulphides and an oxidizing 
agent. Boil the solution and filter. Add BaCl 2 and again filter. 


Precipitate.— 

Filtrate.—Add CaCl 2 and of NaC 2 H 3 0 2 . Filter. 

White, BaS0 4 , 
BaSiF fi . Con¬ 
firm. 

Precipitate.—White, 
CaC 2 0 4 , CaSiO 3 . Yellow, 
CaCr0 4 . Add water and 
boil. 

Filtrate.—Make just alka¬ 
line with Ba(OH ) 2 solution. 


Precipitate.—White indi¬ 
cates any of the following: 
AsO, As0 4 , PO4, BO 3 , C4H4O6, 
S0 3 . Add Br water. A white 
precipitate proves S0 3 . 


Precipitate.— 

CaSiOe. In¬ 

soluble. 

Solution.— 
Yellow, 
CaCr0 4 . 


Soluble Acid Group and Organic Acids 

Members indicated by the H 2 S0 4 acid test. 















SYSTEMATIC ANALYSIS OF A SUBSTANCE 


235 


General Summary of the Acids. 


Acids. 

Detecting Reagents. 

Reactions resulting from Test. 

Acetates 

H 2 S0 4 (cone.) 

Odor of vinegar 

Arsenates 

(a) (NH 4 ) 2 Mo0 4 + HN03 

Yellow precipitate 


(b) Magnesia mixture 

White granular precipitate 


( c ) Reduced on C + Na 2 C0 3 

Garlic odor, arsenic mirror 

Arsenites 

( a ) Magnesia mixture 

No reaction 


(b) H 2 S + HC1 

Yellow precipitate 

Bromides 

(<z) H 2 S0 4 (cone.) 

Red Br vapor 


( b ) Chlorine water+ CS 2 

Reddish color, due to Br 

Borates 

H 2 S0 4 (cone.) + alcohol 

Green flame 

Carbonates 

Dilute acids 

C0 2 evolved. Limewater test 

Chlorates 

(a) H 2 S0 4 (cone ) 

Explosive liberation of Cl + C10 4 


(b) Heated alone 

0 given off 

Chlorides 

AgN0 3 + HN0 3 

White precipitate, sol. inNILOH 

Chromates 

(a) H 2 S0 4 (cone.) 

0 liberated (sol. yellow to green) 


(b) HC1 

Chlorine of HC1 liberated 


(a) Alcohol-fNaOH 

Reduced and Cr(OH) 3 precipi¬ 
tated 

Cyanides 

H 2 S0 4 (cone.) 

HCN (POISON). Odor, bitter 
almonds 

Ferricyanides 

FeS0 4 + HCl 

Turnbull’s blue precipitate 

Ferrocyanides 

FeCl 3 + H Cl 

Prussian blue precipitate 

Fluorides 

H 2 S0 4 (cone.) 

HF gas liberates silicic acid from 
glass rod with drop of H 2 0 

Hypochlorites 

Dilute acids 

Cl liberated, yellow gas 

Iodides 

(a) H 2 S0 4 (cone.) 

Violet vapor of iodine 


(b) Chlorine water+CS 2 

Violet color to CS 2 

Nitrates 

FeS0 4 +H 2 S0 4 (cone.) 

Brown ring 

Nitrites 1 

Dilute acids 

N 2 Os brown evolved 

Oxalates 

H 2 S0 4 (cone.) 

C0 + C0 2 evolved 

Permanganates 

Reducing agents 

Decolorized 

Phosphates 

HNOo+ (NH 4 ) 2 Mo0 4 at 40 0 

Yellow precipitate 

Silicates 

(a) Fused with Na 2 C0 3 and 
HC1 added 

Silicic acid precipitated 


(b) HF 

SiF 4 gas liberated 

Sulphates 

HC1 + BaCl 2 

White precipitate of BaS0 4 

Sulphides 

Dil. acids 

H 2 S gas blackens Pb(C 2 H 8 0 2 )* 

Sulphites 

Dilute acids 

S0 2 gas 

Sulphocyanides 

FeCl 3 

Deep red color 

Thiosulphates 

Dilute acids 

S0 2 gas + free S 

Tartrates 

Ignited 

Char. Odor of burnt sugar 

Organic acids 

Heated 

f 

Generally char. 


* Nitrites + KI + CSj = violet color in CSa due to free I, 















236 


QUALITATIVE ANALYSIS 


Interpretation of Results 

The Unknown in Solution. 

A simple compound in solution offers comparatively little diffi¬ 
culty for interpretation. For example, if the analysis of the cations 
proved silver to be present, and the analysis of the anions showed 
the presence of a nitrate, a report of silver nitrate in solution 
would be correct. In case of hydrolysis, however, such as takes 
place when aluminum sulphide or ferric chloride are dissolved in 
water, the problem offers greater difficulty of interpretation. The 
chemist should have a knowledge of the nature of the substance in 
order to report intelligently on the condition of the substance in 
solution. It is absurd, however, for practical purposes in qualita¬ 
tive analysis, to enter into hair-splitting distinctions. For 
example, in case of the aluminum sulphide in solution, any of 
the following might be present, depending largely on the con¬ 
centration and temperature of the solution: aluminum hydroxide 
undissociated, aluminum sulphide undissociated, aluminum 
cations, hydroxyl anions, hydrogen cations, sulphur anions, undis¬ 
sociated hydrogen sulphide. Furthermore, we are aware that 
aluminum is an amphoteric electrolyte, so that when free inorganic 
acids are added the substance acts as a weak base, and when the 
alkaline bases are added, it acts as a weak acid. 

A mixture of compounds in solution offers an insurmountable 
difficulty for the qualitative analyst, and the problem of determin¬ 
ing how the salts and acids were combined in the dry state is left 
for the quantitative analyst to unravel. Under certain circum¬ 
stances this is impossible. As example of this has already been 
cited in case of the soluble salts, sodium carbonate and potassium 
sulphate, if the gram moles are dissolved in a solution. The 
resulting mixtures would be the same, whether sodium carbonate 
and potassium sulphate were added to, say, one liter of solution, 
or whether sodium sulphate and potassium carbonate were added, 
provided the gram moles were used in each case and other con- 


SYSTEMATIC ANALYSIS OF A SUBSTANCE 


237 


ditions were the same. Hence it is not advisable for the qualita¬ 
tive chemist to attempt a combination of the acid and basic 
radicals in cases of mixed compounds in solution, but simply to 
report the metals and non-metals separately. 

The Unknown as a Solid. 

Simple Compound— The chemist, in dealing with solids, has 
the advantage of a preliminary physical examination and chemical 
tests of the dry substance to aid him in his interpretation of the 
compound. In the case of a single compound the problem appears 
simple, though in reality it may involve a more careful and skillful 
interpretation than one at first would be led to believe. For exam- 
1 pie, if the chemical analysis of the material in solution would prove 
that it contained copper and the acid radical of carbonic acid, 
it does not prove that the substance is copper carbonate, for the 
original material may contain metallic copper, copper oxide in the 
forms CU 2 O and CuO, copper hydroxide Cu(OH) 2 , and copper car¬ 
bonate CUCO3. A physical examination of the solid, however, 
will come to the rescue and enable the chemist to determine 
whether the substance is the homogeneous carbonate or a hetero¬ 
geneous substance containing the compounds mentioned, all of 
which can be recognized in the substance, provided it is not in fine 
powdered form. 

A complex mixture of compounds in solid form offers a more 
difficult problem to solve. The physical examination may throw 
considerable light upon the composition of the heterogeneous sub¬ 
stance, and if it is possible to separately analyze the characteristic 
crystals of which it is composed, the difficulty of the interpretation 
is practically obviated. However, this is not always possible, and 
recourse must be had to certain facts obtained during the chemical 
analysis of the substance. The solubility of the material and the 
reactions during the successive treatment of the material with dif¬ 
ferent solvents frequently throw light upon its composition. The 
problem, however, may be twofold. First, the compounds in water 




238 


QUALITATIVE ANALYSIS 


may form a homogeneous solution when united, or again an inter¬ 
action may take place between the two substances, resulting in less 
soluble compounds being formed. Each of the conditions will be 
taken up briefly. 

Soluble Compounds forming a Homogeneous Solution.—Sup¬ 
pose the mixture is a fine white powder which contains cadmium, 
zinc, and the hydrochloric and carbonic acid radicals. On treat¬ 
ment of the mixture with water, it is found that only a part of the 
powder dissolves, the remainder going into solution upon the addi¬ 
tion of an acid. Since we are aware that nearly all normal car¬ 
bonates are insoluble in water, an analysis of the acid solution will 
determine the metal that is in combination with the carbonate, as 
both zinc and cadmium carbonates are insoluble in water. And 
again, the analysis of the water solution will determine the metal 
in combination with the chloride, since both the metals form 
soluble chlorides. That is to say, if zinc is found in the acid solu¬ 
tion, it evidently exists in the original powder as zinc carbonate, 
and if cadmium is found in the water solution, it exists in the 
powder as a chloride, or vice versa. The oxides and hydroxides 
of these metals will likewise be found in the acid solution, and 
since these are both apt to be white, it is difficult to determine 
whether or not they are present along with the insoluble car¬ 
bonates. 

Soluble Compounds Interacting in Solution.—If an interaction 
takes place when two substances soluble in water are mixed, our 
problem becomes more complex. Take, for example, a mixture of 
potassium carbonate and calcium chloride. Both are soluble in 
water, but when their solutions are mixed, or when water is added 
to their combined solids, a precipitation of calcium carbonate takes 
place. And again, in a mixture of the soluble sodium sulphate 
and the soluble barium chloride, an immediate precipitation of 
barium sulphate takes place when water is added. In such cases 
it is impossible to determine whether barium existed as a sulphate 
in the original substance or whether calcium existed as a carbonate, 


SYSTEMATIC ANALYSIS OF A SUBSTACE 


239 


unless it is possible to separately dissolve a portion of the sodium, 
potassium, calcium, and barium salts and analyze them. It is 
sometimes possible to do this, when the mixture is not in a pow¬ 
dered form, by a primary separation of a few of the characteristic 
crystals. 


240 


QUALITATIVE ANALYSIS 


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REACTIONS OF THE METALS AND ACIDS 


241 



The numerals indicate milligrams of the substance that will dissolve in ioo c.c. of water at stated temperature. Reference to Van Nostrand s Chemi¬ 
cal Annual, edited by Olsen. 
























242 


QUALITATIVE ANALYSIS 


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REACTIONS OF THE METALS AND ACIDS 


243 


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A precipitate forms on long standing. 
























244 QUALITATIVE ANALYSIS 


Soluble Subgroup B. 



Arsenic, As*”, As.. 

Antimony, Sb"', Sb . 


(ous) K 3 As0 3 . 

(ic) KH 2 As0 4 . 

(ous) SbCl 3 . 

(ic) KSb0 3 . 

Hydrogen 

sulphide, 

H 8 S. 

Arsenic trisul¬ 
phide, AS 2 S 3 , 
yellow ppt. Sol. 
in alkalies, 
(NH 4 ) 2 S x , 
(NH 4 ) 2 S. In sol. 
in cone. HC1. 

Arsenic trisul¬ 
phide + S. 

As 2 S 3 + S 2 , yel¬ 
low. The ppt. 
forms slowly by 
heat, 

Antimony trisul¬ 
phide. Sb 2 Sa, 
orange ppt. Sol. 
in alkalies, 

(NH 4 ) 2 S x , 
(NH 4 ) 2 S, HC1 
(cone ). 0.17 mg. 

Antimony penta- 
sulphide, Sb 2 Ss, 
orange ppt. Sol. 
in alkalies, 
(NH 4 ) 2 S x , 
(NH,) 2 S, hci 
( cone.). 

Ammonium 

hydroxide, 

NH 4 OH. 



Antimonious 
hydroxide, 
Sb(OH ) 3 . white 
ppt. Sol. in 
excess. 

Ammonium 

metantimonate, 

NH 4 Sb03. 

Very slightly 
sol. in excess. 

Copper sul¬ 
phate, 

CuS0 4 . 

Copper .arsenite, 
CuHAsC>3 , yel¬ 
lowish green 
ppt. Sol in 
NH 4 OH,NaOH, 
HNO 3 . 

Copper arsenate, 
Cu 3 (As0 4 ) 2 . 
greenish blue 
ppt Sol. in 
NH 4 OH and in 
HN0 3 . 

Antimony oxy¬ 
chloride. white, 
SbOCl. caused 
by dilution. 

Insol alk. 

Sol. HC1, CS 2 . 

Copper antimo- 
nate, brown ppt. 

Mercuric 

chloride, 

HgCl 2 . 

Mercuric arse- 
nite,Hgj(As 03 ) 2 , 
white ppt. Sol. 
in acids. 


Antimony oxy¬ 
chloride, caused 
by dilution. 

Sol. in cone. 

HC1 


Silver ni¬ 
trate, AgNC> 3 . 

Silver arsenite, 
AgaAsOa, yel¬ 
low ppt. Sol. in 
HNO 3 , NH 4 OH, 
HC 2 Hs0 2 . 

Silver arsenate, 
Ag 3 As0 4 , red¬ 
dish brown ppt. 
Sol. in HNOj 
and NH 4 OH. 

Silver chloride 
and antimony 
trioxide, 

AgCl + Sb 2 C>3, 
white ppts. 

Silver antimo- 
nate. Ag 2 Sb0 3 , 
white ppt. Sol. 
in NH 4 OH. 

Miscellany. 

Magnesia mix¬ 
ture. No ppt. 
Arsenic sol. in 
HN0 3 , Cl 2 , 

H 2 0, aq. reg., 
hot alkalies. 

Marsh test 
(Zn+HCl, etc.) 

Magnesia mix¬ 
ture ppts. 
MgNH 4 As0 4 , 
white crys. ppt. 
Sol. in acetic 
acid. 

AsH 3 flame de¬ 
posits arsenic. 
Sol. in NaOCl. 
Sol. in (NH 4 ) 2 S. 
Residue insol. in 
HC1 (cone.). 

KOH ppts. 
Sb(OH) 3 . 
Na 2 C0 3 ppts. 
Sb(OH) 3 . 

Marsh test 
(Zn + HCl). ' 

Sb. sol. in hot 
cone. H 2 S0 4 
and in aq. reg, 

SbH 3 in flame 
deposits anti¬ 
mony. Insol. in 
NaOCl. 


* See Van Nostrand’s Chemical Annual for solubility of salts. 












































REACTIONS OF THE METALS AND ACIDS 


245 


Hydrogen Sulphide Group 


Tin. Sn 

”, Sn"“. 

Platinum, Pt””. 

Gold, Au“*. 

(ous) SnClj. 

(ic) SnCI 4 . 

PtCI 4 . 

AuCl*. 

Stannous sulphide, 
SnS, dark brown. 

Sol in alkalies. 
Difficultly sol. in 
(NH 4 ) 2 S X . Sol. in 
HC1 (cone ), ioo c c 
H 2 0 diss. 0 002 mg. 

Stannic sulphide, 
SnS 2 , yellow ppt. 
Sol. in alkalies, 
(NH 4 ) 2 S X , (NH 4 ) 2 S 
and alkali carbon¬ 
ates. HC1 (cone.). 
H 2 0 =o .02 mg. 

Platinic sulphide, 
PtS 2 , dark hrown 
ppt. Difficultly 
sol. in alkali sul¬ 
phides. Sol. in 
aqua regia Insol 
in HC1 (cone.). 

Gold sulphide, 

Au 2 S 3 , black ppt. 

Sol. in alkali sul¬ 
phides, aqua regia, 
insol in HC1 
(cone.). 

Stannous hydroxide, 
Sn(OH)*. Insol. 

in excess. Darkens 
on cooling. Insol. in 
H 2 0 Sol in dilute 
acids, alk. 

Stannic hydroxide, 
Sn(OH)*. Slightly, 
sol. in excess. 

Ammonium chlo- 
roplatinate. 
(NH 4 ) 2 PtCl 6 , yel¬ 
low ppt. Sol. in 
large excess. 

679 200 mg. 

Fulminating gold, 
Au 2 0 3 . 2 NH 3 , yel¬ 
low ppt., Insol. in 
excess. 

Cuprous chloride, 

2 CuCl, white ppt. 

Sol in acids- 
Reduction by SnClj. 




Mercurous chloride. 
HgCl, white ppt. 
Insol. in cold 

HC1 (cone.). 
Reduction by SnCl 2 . 




Silver chloride and 
silver, AgCl + Ag. 
Reduction by SnCl 2 . 

Silver chloride, 

AgCl. 

Silver chloride and 
platinum oxide, 

AgCl + PtO, 
brown ppt. 

Silver chloride and 
gold oxide, 

AgCl + Au 2 Os, 
brown ppt. 

KOH ppts Sn(OH) 2 , 
NaiC0 3 ppts. 
Sn(OH) 2 . Insol. in 
excess. 

KOH ppts. 

Sn(OH) 4 NaCOs 
ppts. Sn(OH) 2 . 
Insol. in excess. 

'1 

KOH ppts. 

K 2 PtCl 6 . Na 2 C0 8 
gives no ppt. 

Pt sol. in aq. r., 
fused alk. 

SnCl 2 solution 
ppts. “ Purple of 
Cassius,” red ppt. 

Au sol. in KCN, 
aq. reg. 

Metallic Sn depos¬ 
ited by Zn in 

Marsh test. 

Stannic salts 
reduced by H, gen¬ 
erated by Sn. 

Zn ppts. Pt, black, 
from its salts. 

Also see Flectro- 
motive Series p. 10. 

Zn ppts. Au from 
its salts. 



































The Ammonium Sulphide Group. 

Numbers refer to mgs soluble in xoo c c. cold water. 


246 


QUALITATIVE ANALYSIS 













































leddish br< 


REACTIONS OF THE METALS AND ACIDS 


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247 


* Presence of non-volatile organic substances, tartrates, citrates, and sugar prevents precipitation. 




















The Ammonium Sulphide Group — Continued 


248 


QUALITATIVE ANALYSIS 


o 

c n 
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REACTIONS OF THE METALS AND ACIDS 


249 


*5 D 

*5B 
o a 

go az 

"Sb. S.2 
.5 c 2 a 

NNJ3 d 

• T3 
d 

Cu d 

CU c« 

0)3 

«j-~ y 
*5 * 2 

B £3 

§U CO 

D ' w ' "? 

O Z 
c e 2 

nn£.S 

Zinc hydroxide, 

Zn(0H) 2 , white ppt. 

Sol. in excess, forming 

Na 2 Zn0 2 . Repptd. by 

boiling. 

as 

^ o 

Q. C HI? 

CU~ Z 
o-^Z 

3 rt .S 
* 8-g 

. mu rt 

t;3 

CO G3 

MC/5T3 

o5 

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CD #N 

z S =<8 
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5 a c £ 
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o> . o o 

2 3S bn • 

SoO.fi % 

d s' £ o 

SS 2 £ 

•d 

• 2 § 
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S" fi 5 ,, O 

°--p o 11 u 

2 E -2 n « 

3 Z ^ *o 

s q^ * * 

g- 

Cu d "o aI 

Sco’^mzS 

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t*'§l 
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f£ s *$2 

z z a.S z m 

CU 

cu 

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cu — — 

Z co 

HCN ppts. greenish yel¬ 
low, Ni(CN) 2 . Sol in. 
excess. Repptd. by HC1. 
Pptd. by Br + NaOH as 
Ni(OH ) 3 , black +CNBr 
(poison gas). 

U 

as 

s 

<u is 

T3 rj 
•StJ o 

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lug: 

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as 

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For solubility of salts, see tables in D. Van Nostrand's Chemical Annual , edited by Olsen. 























The Ammonium Carbonate Group 

Solubility in milligrams per ioo c.c. of water cold; “c”, and hot, 


250 


QUALITATIVE ANALYSIS 



* Members of the Soluble Metal Groun. 






































REACTIONS OF THE METALS AND ACIDS 


251 


































The Soluble Group. 


252 


QUALITATIVE ANALYSIS 




































REACTIONS OF THE METALS AND ACIDS 


253 





















































REACTIONS OF THE ACIDS. 
Inorganic Acids. 


254 


QUALITATIVE ANALYSIS 





























Chloric H 2 S0 4 , cone. Heated on charcoal deflagrates. 

HClOj,’. warmed with salt H 2 S0 4 evolves yellow gas, C10 2 . 

chlorates .1 causes explosion; 


REACTIONS OF THE METALS AND ACIDS 255 


1 

a 

C 

rt 

* 

uS 

6 c 
c 

OJ 

« <D O 
w _C 

bn o 

0,2 

Cj 

•g J 3 
g.t: 
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<u bJO 

* - c 




a 

co 


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2 ^ s 

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d • 

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o 

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<V rc O 

■SO-g 

hJ O > 


co 

—• 

Cl. 

a 


01 

v L-. ^ 


bC 

a 


4 ?s:z 

w > do 

U | ,N 8 

-o 13 o o 
Ph >^co o 


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co 53 
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J 3 tfl ^ g 

o cL~o <£ 
co a.c/3 «o 


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a 


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X) 

£ £ 
15 £ 
w ”3 

co ^ 

CO 

a ^ 

t. <D 

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CO 

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a. . g 
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c*> ^ f! 

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n l ,h 

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cl, a, co Tt 


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a. 

a. 


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2 

T 3 4 u bb 
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bX) o 00 
Q < co <n 



^ • 
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CO 

#s dJ 

<v 

n3 ^3 

0 * £ 

•*-« a* ctJ 

.2 ^ 

go p 

£.2 

Su 2 


U 32 "5 





Yellow ppt., Agl. 
Very difficultly sol. 
in NH4OH. 

0.03S n ° mg. 

Light yellow ppt., 
AgBr. Difficultly 
sol. in NH4OH. 

| 

. ' i 


u 

• rH 

a 

o 

v- 

43 

O 


CO 

<U 

-O 


s 

p^CQ o 




































Inorganic Acids. 


256 


QUALITATIVE ANALYSIS 












































REACTIONS OF THE METALS AND ACIDS 


257 







































Inorganic Acids. 


258 


QUALITATIVE ANALYSIS 











































REACTIONS OF THE METALS AND ACIDS 


259 























Organic Acids. 


260 


QUALITATIVE ANALYSIS 







































REACTIONS OF THE METALS AND ACIDS 


261 


Melts at 200°. The alkaline solu¬ 
tions absorbs 0 . Limewater or 
Ba(OH) 2 produces a blue ppt. 

Decolorizes KMn 0 4 and 
efferverscence takes place, with 
odor of acetaldehyde. 

Lead acetate ppts. white salt. 

Sol. in hot water. Prevents pption. 
of Fe(OH) 3 by alkalies. 

H 2 S 0 4 (dilute) + Mn 0 2 gives 

C 0 2 . Destroys color of KMn 0 4 
when heated with that reagent iri 

presence of dilute H 2 S 0 4 . 

Lead acetate ppts. a white salt. 

Acid m.p. 156°. 

HN 0 3 heated with salt produces 

yellow picric acid. 

Color is intensified by caustic soda. 

Lead acetate gives a yellow ppt., 

with astringent taste. The acid 

ppts. a solution of glue. Lime- 

water produces a gray ppt. 

Chars when heated. Odor of 

burnt sugar. Prevents pption. of 

Fe(OH)j by alkalies. Silver 

Nitrate test, page 104. 


Charring on heat¬ 
ing with evolution 
of CO. 


Heated. C 0 2 and 
CO evolved. 

Dissolves. Pro¬ 
longed heating 
darkens solution 
and gas 
is evolved. 



Blue-black ppt. 

Sol. in excess = 
green. 




Deep violet 
color. Destroyed 
by mineral acids. 

Blue-black color 
(ink). 




White ppt only in 
presence of strong 
alcohol (distinc¬ 
tion from citric). 

White ppt. Insol. 
in acetic acid. 

Sol. in HC 1 , 

hno 3 . 



White crystalline 
ppt Action simi¬ 
lar to magnesium 
precipitation. 

Metallic Ag from 
reduction 

Reduction results. 
Ag formed (no 
action on 

Fehling’s sol.). 

White ppt. 

White ppt. Sol. in 

hno 3 , nh 4 oh 

0 

is 8 

O.Z U 

4» 55 

.t; 0 0 
£ ^ X 

£.S 0 

White ppt. 

White ppt. Sol. 
in excess of tar¬ 
trate. HC1, 
NH 4 OH. Reduc¬ 
tion on heating. 

X 


N 





o 

o 

X 

X 

O 


X 


J 1 

u 

o 

o 


0 

# 

O 

X 

JO 

o 

•ll 

u 

.. X 
•- % 

if 

a 8 

K 

oO 

cX 

0 32 
•E » 

p * 

O u 

Ji 

rt X 

S u 

X (H 

ox 

*3 * 5 , 

1/5 U 

rt 3 

t-U 

bX 



























262 


QUALITATIVE ANALYSIS 


' Solubility Table. 

Since no salt is absolutely insoluble, the term " insoluble ” is only relative. For solubility 
of the salts formed, see Van Nostrand’s Chemical Annual, edited by Professor John C. Olsen. 


2 

r 1 

Cation. 

u. 

u 

« 

►■H 

Z 

u 

O 

2 

to 

o 

u 

o 

X 

u 

oo 

' ^ 

O 

U 

ec 

O 

(75 

O 

c/o 

-f 

O 

Urn 

u 

OO 

oam 

-*• 

O 

Oh 

o 

CO 

< 

0? 

O 

< 

o 

z 

u 

o 

u. 

'to 

z 

u 
^ — * 
a) 

U. 

A 

V 

K- 

W 

w 

w 

w 

w 

W 

w 

w 

W 

w 

W 

W 

w 

W 

w 

1 w 

w 

W 

W 

,w 

Na* 

vv 

w w 

w 

jw 

W 

w 

w 

w VV 

w 

W 

w 

w 

w 

l w 

w 

W 

w 

w 

Li- 

w 

w 

jw 

vv 

>w 

VV 

w 

w 

w 

w 

w 

W 

w 

w 

w 

r w 

w 

w 

w 

w 

Ba” 

wa 

w 

w 

W wA 

w w 

w 

w 

A 

A 

I 

A 

A 

A 

A 

A 

— 

wA 

— 

Sr* 

wa 

w 

w 

VV 

1 w ,w w 

w 

vv 

A 

A 

I 

wA 

A 

A 

A 

A 

— 

W 

— 

Ca” 

wa 

w 

w 

w 

i w w 

vv 

vv 

w 

A 

A 

wa 

wA 

A 

A 

A 

A 

w 

W 

— 

Mg- 

wa 

w 

w 

w 

w 

w 

VV wA W 

A 

A 

W 

W 

wA 

A 

A 

A 

w 

w 

— 

AT“ 

W 

w 

w 

w,- 

vv 

w 

vv 

— 

— 

wa 

W 


A 

A 

A 

— 

— 

— 

— 

Mn" 

A 

w 

w 

w 

a; 

w 

W wA 

A 

A 

A 

W 

W 

A 

A 

A 

A 

I 

A 

— 

Zn- „ 

wA W 

w 

w 

A 

w 

w 

w 

A 

A 

A 

W 

VV 

A 

A 

A 

— 

A 

wa 

— 

Cr- 

W 

ww 

w 

A 

w 

W wA 

— 

— 

A 

w 

A 

A 

A 

A 

— 

— 

— 

_ 

Cd- ' 

wA 

w 

w 

W; A 

w 

W 

w 

A 

A 

A 

w' 

W 

wA- 

A 

— 

— 

- - 

— 

_ 

Fe- 

wA 

ww 

W 

wa 

w 

w 

w 

A 

A 

A 

vv' 

— 

A 

A 

A 

A 

I 

I 

_ 

Fe-. 

W 

w 

w 

— 

— W 

vV 

A 

— 

— 

A 

w 

W 

A 

A 

A 

A 

w 

I 

— 

Co- 

wA W 

w 

w 

wa W 

W 

w 

A 

A 

A 

w 1 

A 

A 

A 

A 

A 

I 

I 

_ 

Ni- 

wA 1 W 

w 

w 

wa 

w 

VV 

w 

A 

A 

A 

vv 

A 

A 

A 

A 

A 

I 

I 

_ 

Sn” 

W 

w 

-! 

w 

— ; 

w w, 

A 

A 

— 

— 

w 

A 

A 

A 

— 

— 

I 

I 

_ 

.Sn— 

W 

w 

— 

w 

i 

J 

1 


A 






A 

A 

A 

_ 

I 

_ 

Pb- 

A 

w w 

w 

A 

w 

w 

w 

A' 

A 

A 

I 

I 

A 

A 

A 


wA 

A 

_ 

Cu” 

A 

w 

w 

I 

I ,W 

w 

w 

A 

A 

— 

w 

W 

A 

A 

A 

A 

_ 

I 

_ 

Sb- 

W 

A ; 

A 

wA 

— 

— 1 

— 

A 

A 

— 

—- 

A 

A 

_ 

A 

A 

_ 

_ 

_ 

_ 

Bi- 

W 

A 

A- 

A 

— 

A 

w 

A 

A 

A 

A 

A 

A 

A 

A 

A 

*_ 

_ 

_ 

_ 

Hg* 

r- 

I 

I 

I 

— 

w 

w ! 

A 

— 

A 


wA 

A 

— 

A 

A 

A 

_ 

_ 

_ 

Hg" 

wA 

W 

w 

A 

W 

w 

vv 

A 

A 

A 

— 

W wA 

— 

A 

A 

A 

— 


_ 

A g‘ 

W 

I 

I 

1 

I 

w 

w 

A 

A 

A 

A 

wA 

A 

A 

A 

A 

A 

A 

I 


Pt— 

— 

w 

t 

w 

I 

w 

w 















Au” 

— 

w 

w 

A 

w 




i 










•• 



Abbreviations. — W = soluble in water; A = soluble ip acids; wA slightly soluble 
in water, readily soluble in acids; wa = difficultly soluble in water and in acids; I = insol* 
Vble in water and acids. 

The metals are arranged In order of their electromotive series. 














































































263 


’ REACTIONS OF THE METALS AND ACIDS 
INTERNATIONAL ATOMIC WEIGHTS, 1920 


ATOMIC 

WEIGHT. 


ELEMENT. 


ATOMIC 

WEIGHT. 


Aluminum. 

\ntimony. 

4rgon. 

Arsenic. 

Barium. 

Bismuth. 

Boron. 

Bromine. 

Cadmium. 

Gaesium. 

Galcium. 

Carbon. 

jGerium. 

Chlorine. 

Chromium. 

Cobalt. 

Golumbium. 

popper... 

Dysprosium. . . . 

Erbium. 

Europium. 

Fluorine. 

Gadolinium. 

Gallium. 

Germanium. 

Glucinum. 

Gold. 

Helium. 

Holmium. 

Hydrogen. 

[ndium. 

Iodine. 

Iridium. 

Iron. 

Krypton. 

Lanthanum. 

Lead. 

Lithium. 

Lutecium. 

Magnesium. 

Manganese. 

Mercury. 


A1 

27.1 

Sb 

120.2 

A 

39.90 

As 

74.96 

Ba 

137.37 

Bi 

208.0 

B 

10.9 

Br 

79.92 

Cd 

112.40 

Cs 

132.81 

Ca 

40.07 

C 

12.005 

Ce 

140.25 

Cl 

35.46 

Cr 

52.0 

Co 

58.97 

Cb 

93.1 

Cu 

63.57 

Dy 

162.5 

Er 

167.7 

Eu 

152.0 

F 

19.0 

Gd 

157.3 

Ga 

70.1 

Ge 

72.5 

G1 

9.1 

Au 

197.2 

He 

4.0 

Ho 

163.5 

H 

1.008 

In 

114.8 

I 

126.92 

Ir 

193.1 

Fe 

55.84 

Kr 

82.92 

La 

139.00 

Pb 

207.20 

Li 

6.94 

Lu 

175.0 

Mg 

24.32 

Mn 

54.93 

Hg 

200.6 


Molybdenum. . . 
Neodymium.... 

Neon. 

Nickel. 

Niton. 

Nitrogen. 

Osmium. 

Oxygen. 

Palladium. 

Phosphorus. 

Platinum. 

Potassium.. 

Praseodymium.. 

Radium. 

Rhodium. 

Rubidium. 

Ruthenium. 

Samarium. 

Scandium. 

Selenium. 

Silicon. 

Silver. 

Sodium. 

Strontium. 

Sulphur. 

Tantalum. 

Tellurium. 

Terbium. 

Thallium. 

Thorium. 

Thullium. 

Tin.... 

Titanium. 

Tungsten. 

Uranium. 

Vanadium. 

Xenon.. 

Ytterbium. 

Yttrium. 

Zinc... 

Zirconium. 


Mo 

96.0 

Nd 

144.3 

Ne 

20.2 

Ni 

58.68 

Nt 

222.4 

N 

14.008 

Os 

190.9 

O 

16.00 

Pd 

106.7 

P 

31.04 

Pt 

195.2 

K 

39.10 

Pr 

140.9 

Ra 

226.0 

Rh 

102.9 

Rb 

85.45 

Ru 

101.7 

Sa 

150.4 

Sc 

44.1 

Se 

79.2 

Si 

28.3 

Ag 

107.88 

Na 

23.00 

Sr 

87.63 

S 

32.06 

Ta 

181.5 

Te 

127.5 

Tb 

159.2 

T1 

204.0 

Th 

232.15 

Tm 

168.5 

Sn 

118.7 

Ti 

48.1 

W 

184.0 

U 

238.2 

V 

51.0 

Xe 

130.2 

Yb 

173.5 

Yt 

89.33 

Zn 

65.37 

Zr 

90.6 




























































































INORGANIC COMPOUNDS 


264 


QUALITATIVE ANALYSIS 













































































INORGANIC COMPOUNDS 


265 


G 

to 

Q3 


03 

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to 

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TO Q, 

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cc <d 

to *-» 

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a> 03 

a m 

JJ T3 
* 515 






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* Color. —Colorless crystalline compounds appear white in powdered form or as precipitated from a solution. When 
the color of the substance is omitted white is understood. 

Acknowledgment is made to D. Van Nostrand, “Chemical Annual,’’ 1918 edition, Edited by J. C. Olsen, for the list 
of compounds given in this section. 









































































INORGANIC COMPOUNDS —Continued 


266 


QUALITATIVE ANALYSIS 


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INORGANIC COMPOUNDS 

i 


267 


• cJ 
© M 

*n 'o 

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a 

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to 

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INORGANIC COMPOUNDS —Continued 


278 


QUALITATIVE ANALYSIS 


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sulphate.Na 2 S0 4 .4.8°° 42.5 100 ° insoluble alcohol.rhomb, monel. 

or hexagonal 

sulphide mono- .Na 2 S..15.4 10 ° 59.2 90 * s. sol. al.; insol. ether.. . flesh col. amo. 

















































































































INORGANIC COMPOUNDS —Continued 


288 


QUALITATIVE ANALYSIS 


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INORGANIC COMPOUNDS 


289 


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INORGANIC COMPOUNDS —Continued 


290 


QUALITATIVE ANALYSIS 


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PART VI 


THE LESS COMMON ELEMENTS 

RARER ELEMENTS OF THE HYDROGEN SULPHIDE GROUP 

GOLD 

Au, at.wt. 197.2; sp.gr. 19.33; m.p.1063; b.p.2530°C.; oxides, Au 2 0, Au 2 0 3 . 

Gold is a soft, malleable, ductile, yellow metal. It appears red or bluish 
violet in finely divided form. It is precipitated from solution as a dark brown 
powder. Gold forms two series of compounds, aurous and auric. 

Solubility.—Gold in massive form is practically insoluble in pure nitric, 
sulphuric or hydrochloric acids, but in the presence of oxidizing agents, is 
attacked appreciably by sulphuric, and actively by hydrochloric acid. Gold 
a found in minute quantity in the nitric acid solution of its alloys, and in such 
is contain selenium, the amount may be a large part of the total alloy present. 

Gold is attacked energetically by aqua regia. Large amounts of gold are 
lissolved with requirement of least attention when the proportion of hydro¬ 
chloric acid is several times that of the aqua regia formula, (3HC1 : 1HN0 S ). 

Gold is dissolved by solutions of chlorine or bromine, by alkaline thio- 
;ulphates; in the presence of free oxygen by iodine in potassium iodide solu- 
ion, by soluble cyanides, by fused potassium or sodium hydroxide; by fused 
jotassium or sodium nitrate or sulphide. In a finely divided state, it is dis- 
olved by a solution of potassium or sodium hydroxide. 

Gold alloys quickly with molten lead. When in the form of bright, untar- 
lished particles it alloys readily with mercury. 

DETECTION 

Because of the limited application and tediousness of wet methods, the 
letection of a small quantity (2 parts per million or less) of gold in a mineral or 
>ase metal is most positively carried out by furnace methods of assaying. 
Vet methods of detection of traces of gold can be applied only to solutions 
ree of colored salts and elements precipitated by the reagents employed. As 
rule, in the treatment of an unknown substance, advantage is taken of the 
olubility of most metals and their compounds, and insolubility of gold by 
ne of the mineral acids. 


293 




294 


QUALITATIVE ANALYSIS 


Detection of Gold in Alloys.—In metals or alloys which produce colorles 
solutions with dilute nitric acid, gold, in the absence of other insoluble mattei 
appears as a black or brownish residue which settles readily, and from whicl 
the liquid can be Separated by careful decantation. If unassociated wit] 
metals of the platinum group, this residue will become yellowish brown oi 
heating with strong nitric acid. 

In copper, nickel and such alloys, which leave a residue of sulphur, carboi 
or silicious matter on treatment with dilute nitric acid, the solution is filters 
through double ashless filters and the filter and residue incinerated in 
porcelain crucible. The residue, which may require pulverizing, is digested 
for a few minutes with aqua regia, and the dilute, filtered solution evaporate 
to dryness by heating below 200° F. Just as soon as dry, the mass is moist 
ened with the least quantity of hydrochloric acid and the purple of Cassiu 
test applied to its water solution in a small volume. This test is made b; 
adding a solution of stannous chloride, containing stannic chloride. I: 
strongly acid and concentrated gold solutions a precipitate of brown metalli 
gold is obtained. If the solution is but slightly acid and dilute, a reddis! 
purple color is produced by colloidal gold and the stannic acid. The tin 
fades on standing. Addition of ammonia produces a red coloration. 

This test applied to 1 part of gold in 600,000 of solution will impart a pei 
ceptible shade; to double this quantity, a mauve color. When gold is presen 
in somewhat greater proportion a flocculent precipitate will form. 

Test for Gold in Minerals.—From minerals, in which the metal exists i 
unalloyed, or uncombined state, gold may be extracted by iodine in potassiur 
iodide solution, or by chlorine or bromine water. All minerals containin 
sulphides should be roasted. In natural or roasted state the sample shoul 
be very finely pulverized, and usually yields the gold best if first digeste 
with nitric acid and washed free of soluble salts. The sample in a flask i 
covered with bromine water, the flask closed with a plug and shaken frequentl 
during a period of three or four hours. The purple of Cassius test is applie 
to the extract, removed by decantation after concentration. 

If it is evident that base metals are present in the bromine water extrac 
in quantity sufficient to mask the purple of Cassius test, hydrogen peroxid 
is added to the concentrated liquid, slightly alkaline with sodium or potassiur 
hydroxide or carbonate. After boiling the solution until hydrogen peroxid 
is removed, precipitated hydroxides or carbonates are dissolved by hydro 
chloric acid. Gold in exceedingly small quantity exhibits itself as a lighl 
brown residue in a fine filter. This indication should be confirmed by a purp] 
of Cassius test on the aqua regia solution of the residue; the test carried oi 
in the same manner as on the residue from a solution of a metal. 

Benzidine Acetate Tests.—Male testa and Nola make use of benzidir 


THE LESS COMMON ELEMENTS 


295 


icetate (1 gram benzidine dissolved in 10 cc. acetic acid and 50 cc. water) 
is a reagent in the detection of gold and platinum in quite dilute solutions, 
jrold gives a blue coloration which gradually changes to violet. The colora- 
,ion is green in the presence of free acetic acid, changing to blue with addition 
)f benzidine in excess. Platinum gives a blue flocculent precipitate, the 
ormation of which is promoted by heating. Free mineral acids have no 
nfluence on the gold and retard the platinum reaction only in the cold. Since 
erric salts give a blue coloration, stable only in excess of benzidine, their 
tbsence must be assured before application of the test for the precious metals. 
The limit of sensitiveness of the test is 35 parts for gold and 125 parts for 
ilatinum per 10,000,000. 

Phenylhydrazine Acetate Test.—E. Pozzi Escot adds phenylhydrazine 
icetate to a very dilute gold solution which contains an excess of an organic 
icid (formic or citric). A violet coloration, permanent for several hours, is 
mparted. The depth of color is proportional to the quantity when the gold 
s present in less amount than one part in 500,000. 


PLATINUM 

Pt, at.wt. 195.2; sp.gr. 21.48; m.p. 1755° C.; oxides PtO, Pt0 2 . 

Platinum is a gray, lustrous, soft and malleable metal. It is not altered by 
rnition in the air, but fuses in the oxy-hydrogen flame. It does not dissolve 
i any of the single acids, but a fusion with acid potassium sulphate attacks 
he metal slowly. The action of chlorine in general, and nitro-hydrochloric 
cid (aqua regia), the main solvent, converts the metal to hydrochlorplatinic 
cid, H 2 PtCle, which forms many double salts, or platinochlorides. If platimc 
hloride is gently heated it breaks up into platinous chloride, PtCl 2 , and 

hlorine. . . .. 

Platinum alloyed with silver, may be dissolved by nitric acid to a yellow 
[quid, provided sufficient silver is present in the alloy. Platinum forms 
usible alloys with arsenic, antimony, phosphorus, boron, silicon, and most 
if the metals; hence these'metals, and readily reducible compounds, should 
L ot be heated in platinum vessels. The coefficient of expansion is the same 
,s that of glass, so that a platinum wire can readily be sealed into a glass rod. 
Since the metal may be either divalent or tetravalent, it has two senes of 
ompounds. 

Platinum may be present under the following conditions: 

1. Native grains usually accompanied by the other so-called platinum 









296 


QUALITATIVE ANALYSIS 


metals, iridium, palladium, ruthenium, rhodium, and osmium, together with 
gold and silver (alloyed with one or more of the allied metals). 

Ore concentrates containing the native grains, as above, with the base 
metals, iron, copper, chromium, titanium, etc. The associated minerals 
high in specific gravity in the gravels may be expected to appear with the 
platinum nuggets, such as chromite, magnetite, garnet, zircon, rutile, small 
diamonds, topaz, quartz, cassiterite, pyrite, epidote, and serpentine; with 
gold in syenite; ores of lead and silver. 

2. Scrap platinum containing, oftentimes, palladium, iridium, gold, silver 
and iron. 

3. Small amounts of platinum in the presence of large amounts of iron, 
silica, carbon, magnesia: platinum, residues, nickel and platinum contacts, 
photography paper, jewelers’ filings and trimmings, dental and jewelers’ 
sweeps and asbestos, etc. 

4. Platinum alloyed with silver, gold, tungsten, nickel, copper, lead, etc. 

5. Platinum solutions and salts. 

Solubility.—The best solvent for platinum is aqua regia. The metal is 
also acted upon by fusion with the fixed alkalies—sodium or potassium hydrox¬ 
ide and sodium peroxide or potassium or sodium nitrate; also by fusion 
with acid potassium sulphate. The element dissolves in nitric acid when 
alloyed with a sufficient amount of silver (distinction from gold). 

All salts of platinum are soluble in water. The less .soluble salts are the 
chloroplatinates of potassium, ammonium, rubidium and caesium. Heat 
increases the solubility, while the presence of alcohol decreases the solubility. 

DETECTION 

Ammonium chloride added to a concentrated solution of platinum chloride 
precipitates yellow (NH 4 ) 2 PtCl 6 , which is slightly soluble in water, but insol¬ 
uble in dilute ammonium chloride solution and alcohol. 

Ferrous sulphate precipitates metallic platinum on boiling from a neutral 
solution. Neutralize with Na 2 C0 3 . Free mineral acids prevent the precipi¬ 
tation (different from gold). 

Formic acid precipitates from neutral boiling solutions all the platinum as 
a black metallic powder. 

Hydrogen sulphide precipitates black platinum disulphide, PtS 2 , with the 
other elements of the hydrogen sulphide group. The solution should be warm, 
as precipitation takes place more quickly. It is difficultly soluble in ammo¬ 
nium sulphide. It will be found in the extract with the arsenic, antimony, 
tin, gold, molybdenum, etc., and is precipitated with these elements upon 
addition of hydrochloric acid. Platinum sulphide is soluble in aqua regia. 

Oxalic acid does not precipitate platinum (difference from gold). 


THE LESS COMMON ELEMENTS 


297 


Potassium chloride precipitates yellow K 2 PtCl 6 , which is difficultly soluble 
in water, but insoluble in 75 per cent alcohol. 

Potassium iodide precipitates platinum iodide, but it dissolves quite 
readily, giving a pink to a dark blood-red liquid, depending on the concen¬ 
tration of the solution. Nitric acid should be absent. Heat destroys this 
jolor, as well as hydrogen sulphide, sodium thiosulphate and sulphite, sul- 
ihurous acid, mercuric chloride and certain other reagents. 

Sodium hydroxide with glycerine reduces hydrochlorplatinic acid on warni¬ 
ng to black metallic powder. 

Stannous chloride does not reduce platinum chloride to metal, but reduces 
lydrochlorplatinic acid to hydrochlorplatinous acid. 

H 2 PtCl 6 +SnCl 2 = H 2 PtCl 4 +SnCl 4 . 

Metallic zinc, magnesium, iron, aluminum and copper are the most im¬ 
portant metals that precipitate metallic platinum. 

H 2 PtCl6+3Zn = 3ZnCl 2 +H 2 +Pt. 







298 


QUALITATIVE ANALYSIS 


RARER ELEMENTS OF THE ALLIED PLATINUM METALS 

IRIDIUM 

Element, Iridium. Ir. at.wt. 193.1; sp.gr. 22.3; m.p. 2350° C.? oxid( 

IrCU, Ir 2 O 3 . 

Iridium is found associated with platinum. The element is insoluble in j 
acids, including aqua regia. Chlorine is the best reagent which forms tl 
chlorides of iridium and yields compounds with other chlorides as K 3 IrC 
which is insoluble. If the element is heated in a stream of chlorine in tl 
presence of potassium chloride there forms a salt, K^IrCL, which is sparing 
soluble and is used in the separation of iridium. • 

Substances in which iridium is determined are few, namely: platinu 
scrap, jewelers’ sweeps, contact points, ores, etc. 

Solution of Iridium Alloys.—Platinum scrap and contact points, eti 
containing iridium dissolve with difficulty in aqua regia, depending on tl 
amount of iridium present. The alloy is dissolved quicker if it is rolled 
)hammered to a very thin sheet or ribbon. The alloy of platinum and iridiu 
with an iridium content up to 10 per cent dissolves in aqua regia slowly; j 
■alloy of iridium content of 15 per cent dissolves in aqua regia very slow 
and the aqua regia will likely have to be replenished from time to time. 1 
alloy of 25 per cent iridium is practically insoluble in aqua regia. The filin 
from the sweeps, etc., can be dissolved by aqua regia the same as the scrap. 

DETECTION 

Caustic Alkalies produce in a boiling solution a dark-blue precipitate 
Ir(OH) 4 insoluble in all acids except HC1. 

Potassium chloride forms the double salt of K^IrCle, which is black and 
difficultly soluble in water. 

Ammonium chloride precipitates black (NH 4 ) 2 lrCl 6 , which is difficult 
soluble in water. 

Hydrogen sulphide precipitates black Ir 2 S 3 , soluble in (NH 4 ) 2 S. 

Metallic zinc precipitates from an acid solution black metallic iridium. 

Formic acid and sulphurous acid precipitate black metallic iridium frc 
hot solutions, 



299 


THE LESS COMMON ELEMENTS 
OSMIUM 

lement, Osmium. Os, at.wt. 190.9; sp.gr. 22A; m.p. 2700° C.? oxides 
OsO, 0s 2 0 3 , 0s0 2 , QsO 4. 

Osmium occurs with platinum ores and alloyed with iridium. The chlo- 
des, OsCl 2 and OsCl 4 , combine with the alkali chlorides. Osmium oxidizes 
isily and bums in the flame. Through the action of HN0 3 , aqua regia or 
sating in a stream of moist chlorine, osmic tetroxide is formed. Osmium 
very volatile and the fumes are poisonous. It is detected readily by the 
lor when heated, as the fumes are highly corrosive and disagreeable like 
llorine. Chlorine passed over hot osmium mixed with KC1 gives K 2 0sC 1 6 , 
hich dissolves in cold water. 

Osmium is estimated mainly in osmiridium and platinum residues. 

; Solution.—After the platinum is extracted the residue or osmiridium is 
ixed with two or three times its weight of common table salt. The mixture 
put in a porcelain or silica tube and heated to a dull red heat; moist chlorine 
then passed through the tube for a short time. The mass is cooled and 
ssolved with water. After several treatments the entire group of platinum 
j.etals will be in solution. 

, The osmium material may also be fused with KOH and KN0 3 and the-; 
elt dissolved in water. The osmium will be in solution as potassium: 
smate, K 2 0 s 0 4 , while the iridium remains as residue. 

DETECTION 

Hydrogen sulphide precipitates brownish black osmium sulphide, OsSY* 
ut only in the presence of some strong mineral acid. It is insoluble in ammo- 
fium sulphide. 

Potassium hydroxide precipitates reddish-brown osmium hydroxide.. 

Ammonium hydroxide precipitates the osmium hydroxide. 

, Zinc and formic acid precipitate black metallic osmium. 

Hydrogen reduces osmium compounds to the metal. 


PALLADIUM 

lement, Palladium. Pd. at.wt. 106.7; sp.gr. 11.9s m.p. 1549* C.; oxides 

Pd 2 0, PdO, Pd0 2 . 

This metal is also found associated with platinum and iridium as well as 
athenium, rhodium, and osmium. It occurs in the metallic state sometimes 
kth gold and silver. It resembles platinum as to lustre and color. Palladium 


) 











300 


QUALITATIVE ANALYSIS 


sponge when heated slightly gives a rainbow effect due to the formation of 
oxides. Hydrogen passed over the sponge restores it to the original color. 

Palladium is determined in alloys, ores, jewelers’ sweeps, etc. 

It dissolves in HNO 3 and boiling H 2 SO 4 . HC1 has little action upon it. 
It is readily soluble in aqua regia, forming PdCl 2 . Palladium when alloyed 
with platinum, or an alloy of platinum, iridium and palladium, dissolves 
with the other metals in aqua regia as the chloride. When palladium is 
alloyed with silver the palladium and silver are dissolved in HN0 3 . 

Compounds of Palladium. Soluble.—Chloride, PdCl 2 2H 2 0 red brown; 
nitrate, Pd(N0 3 ) 2 , brown; sulphate, PdS0 4 -2H 2 0 brown; Insoluble- 
bromide, PdBr 2 , brown; cyanide, Pd(CN) 2 , yellow; iodide, Pdl 2 , black; 
Oxides, Pd 2 0, PdO, Pd0 2 , black; sulphides, Pd 2 S, gray; PdS, black. 

DETECTION 

Alkalies precipitate a dark-brown precipitate soluble in excess of the 
reagent. If boiled a brown palladous hydroxide is precipitated. The anhy¬ 
drous oxide is black. 

Ammonia gives a flesh-red precipitate, PdCl 2 NH 3 , soluble in excess of 
ammonia. If HC1 is added to this solution the yellow compound of pallad- 
ammonium chloride, Pd(NH 3 Cl) 2 , is deposited. 

Ammonium chloride precipitates palladium as (NH 4 ) 2 PdCl 4 from the 
nitrate. 

Ferrous sulphate slowly produces a black precipitate of metallic palladium 
from the nitrate. 

Formic acid, zinc and iron literate to metallic palladium from its solutions. 

Hydrogen sulphide precipitates black palladous sulphide, PdS, soluble in 
HC1 and aqua regia, but insoluble in (NH 4 ) 2 S. 

Mercuric cyanide precipitates a yellowish-white gelatinous precipitate, 
Pd(CN) 2 , insoluble in dilute acids, but dissolving in ammonia and in potassium 
cyanide to K 2 Pd(CN) 4 . 

Potassium iodide precipitates black palladous iodide, Pdl 2 , insoluble in 
water, alcohol, and ether, but soluble in an excess of the reagent. 

Potassium nitrite precipitates a yellow crystalline powder, K 2 Pd(N0 2 )4. 


THE LESS COMMON ELEMENTS 


301 


RHODIUM 

Element, Rhodium. Rh, at.wt. 102.9; sp.gr. 12.1; m.p. I960® C.; ojrides 

RhO, Rh^O.i, Rh02. 


Rhodium is found only in platinum ores. It is a white metal, difficultly 
fusible, and insoluble in acids. Rhodium, however, dissolves in aqua regia 
when alloyed with platinum, to a cherry-red solution. It is also soluble in 
molten phosphoric acid and dissolves when fused with acid potassium sulphate 
with the formation of K 3 Rh(S0 4 )3. If the metal is treated with chlorine 
in the presence of sodium chloride there forms a soluble salt, Na 3 RhCl6. 

Rhodium is estimated mainly in ores, thermo couples and salts. 

Solution of Alloys.—When rhodium is estimated in thermo couples or 
other alloys of platinum and rhodium the wire or sample is rolled to a thin 
ribbon and dissolved in aqua regia. Both metals will go into solution, forming 
the chlorides of rhodium and platinum. The aqua regia will have to be 
replaced from time to time, as the alloy dissolves slowly. 

The rhodium from salts is precipitated with zinc and the black metallic 
rhodium cleaned with dilute aqua regia, filtered, washed, ignited and reduced 
with hydrogen. 

Some alloys and ores are alloyed with silver and the silver and platinum are 
dissolved in HN0 3 . Rhodium is in the residue. 

DETECTION 

Hydrogen sulphide precipitates from a hot solution and incompletely a 
brown rhodium sulphide, Rh 2 S 3 . 

Potassium hydroxide precipitates at first a yellow hydroxide, Rh(OH) 3 
+H 2 0 soluble in an excess of the reagent. If boiled, a gelatinous, dark- 
brown hydroxide, Rh(OH) 3 , separates. A solution of Na 3 RhCl 6 does not 
show this reaction immediately, but the precipitate appears in the course of 
time. An addition of alcohol causes a black hydroxide to be precipitated 

at< Ammonium hydroxide produces a yellow precipitate of Rh(NH 3 ) 6 Cl 3 
which is insoluble in HC1. 

Potassium nitrite precipitates from hot solutions a bright yellow precipi- 
tate of double nitrite of potassium and rhodium. 

Zinc, iron and formic acid precipitate rhodium as a black metal. 

Hydrogen reduces rhodium salts. 





302 QUALITATIVE ANALYSIS 

RUTHENIUM 

Element, Ruthenium. Ru. at.wt. 101.7; sp.gr. 12; m.p. 2450° C.? oxides 
RuO, Ru 2 0 3 , Ru0 3 , Ru0 4 . 

This element is found only in platinum ores. It is barely soluble in aqua 
regia, and insoluble in acid potassium sulphate. It dissolves when fused 
with KOH and KN0 3 . The solution of the fusion when dissolved in water 
forms potassium rutheniate, K 2 Ru0 4 , from which HN0 3 precipitates the 
hydroxide, which is soluble in HC1. The treatment with chlorine and KC1 
at a high temperature yields a salt of K 2 RuC 1 6 . The - salts that are most com¬ 
mon are X 2 RuCh and K 2 RuC1 6 . 

Ruthenium is generally estimated in alloys and ores or residues. 

Solution of Alloys.—When ruthenium is alloyed with platinum or gold, 
aqua regia dissolves these metals, forming the chlorides of platinum, gold 
and ruthenium. The ruthenium in ores is in the form of an alloy with plati¬ 
num or osmiridium. This is fused with KN0 3 and KOH in a silver crucible, 
the osmium and the ruthenium forming salts while the iridium remains as an 
oxide. 

DETECTION 

Potassium hydroxide precipitates a black hydroxide easily soluble in HC1. 

Hydrogen sulphide slowly produces black Ru 2 S 3 . 

Ammonium sulphide precipitates brownish black sulphide. 

Metallic zinc precipitates metallic ruthenium, the solution first turning 
blue. 


THE LESS COMMON ELEMENTS 


303 


MOLYBDENUM 

Mo, at.wt. 96.0; sp.gr. 8.6-9.01; m.p. 2500° C.; oxides, M 2 0 3 , Mo0 2 , MoO s . 

Metallic molybdenum is softer than steel, malleable and capable of being 
forged and welded. The metal combines with the halogens to form a number 
of salts. It forms compounds with phosphorus, boron, silicon, sulphur, 
carbon, and alloys with iron and other metals. 

The determination is required in the ores—molybdenite, MoS 2 (60 per 
cent Mo;) molybdite, M 0 O 3 (straw yellow); wulfenite, PbMo0 4 (yellow, bright 
red, olive green or colorless); Ilsemannite, M 0 O 3 + M 0 O 2 ; powellite, CaMo0 4 ; 
pateraite, CoMo0 4 ; belonesite, MgMo0 4 ; eosite, lead-vanado-molybdate; 
achromatite, lead molybdate and arsenate with tin oxide and lead chloride. 
Some iron and copper ores also contain molybdenum. 

The metal is determined in certain self-hardening steels and alloys. 

The reagents ammonium molybdate and the oxide-molybdic acid, M 0 O 3 , 
are valuable for analytical purposes. 

Solubility.—In dissolving the substance the following facts should be 
kept in mind: The metal is easily soluble in aqua regia; soluble in hot con¬ 
centrated sulphuric acid, soluble in dilute nitric acid, oxidized by excess to 
M 0 O 3 . It is dissolved by fusion with sodium carbonate and potassium 
nitrate mixture. It is insoluble in hydrochloric, hydrofluoric and dilute 
sulphuric acids. 

The oxide M 0 O 3 is but slightly soluble in acids and alkalies; M 0 O 2 is insolu¬ 
ble in hydrochloric and hydrofluoric acids. M 0 O 3 , as ordinarily precipitated, 
is soluble in inorganic acids and in alkalies. The oxide sublimed is difficultly 
soluble. 

Molybdates of the heavy metals are insoluble in water, the alkali molyb¬ 
dates are soluble. 

Ores.—Molybdenum ores are best decomposed by fusion with a mixture 
of sodium carbonate and potassium nitrate. The cooled fusion is then 
extracted with hydrochloric acid. 

Steel and Iron—The drillings are dissolved in a mixture of hydrochloric 
and nitric acid (25 cc. HC1+1 cc. HNO 3 ), with gentle heating. Additional 
nitric acid is added if required or potassium chlorate may be used to oxidize 
the iron. 

DETECTION 

Molybdenum appears in the hydrogen sulphide group, being precipi¬ 
tated by H 2 S in acid solution as the sulphide. It passes into solution by 
digestion with ammonium sulphide or sodium sulphide along with arsenic, 
antimony, tin, gold and platinum. By addition of metallic zinc, antimony, 





304 


QUALITATIVE ANALYSIS 


together with tin, gold and platinum are precipitated as metals while 
molybdenum remains in solution. Arsenic, that has not volatilized as 
arsine, is expelled by evaporation. Nitric acid is now added and the solu¬ 
tion taken to dryness. Molybdenum is extracted from the residue with 
ammonium hydroxide. 

A dilute solution of ammonium molybdate treated with a soluble 
sulphide gives a blue solution. 

Sodium thiosulphate added to a slightly acid solution of ammonium 
molybdate produces a blue precipitate with a supernatant blue solution. 
With more acid a brown precipitate is formed. 

Sulphur dioxide produces a bluish-green precipitate if sufficient molyb¬ 
denum is present, or a colored solution with small amounts. The reducing 
agents, stannous chloride, or zinc in acid solution, produce a play of colors 
when they react with molybdenum solutions, due to the formation of the 
lower oxides. The solution becomes blue, changing to green, brown and 
yellow. 

Molybdenum present as molybdate is precipitated by disodium phos¬ 
phate as yellow ammonium phosphomolybdate from a nitric acid solution. 
The precipitate is soluble in ammonium hydroxide. 

A pinch of powdered mineral on a porcelain lid, moistened with a few 
drops of strong sulphuric acid, stirred and heated to fumes, then cooled 
will produce a blue color when breathed upon. The color disappears or 
heating, but reappears on cooling. Water destroys the color. 

Molybdenite is very similar to graphite in appearance. It is distin¬ 
guished from it by the fact that nitric acid reacts with molybdenite, MoS 2 
leaving a white residue, but has no action upon graphite. The blowpip< 
gives SO 2 with molybdenite and C0 2 with graphite, 


SELENIUM AND TELLURIUM 


Se 8 at.wt. 79.2; sp.gr. 


f amorphous 4.26; m.p. 217°; \ 
l crystalline 4.82; i 

Se0 2 ; acids, H 2 Se0 3 , H 2 Se0 4 . 


b.p. 


690°C.; 


oxid< 


Te, at.wt. 127.6; sp.gr. 6.27; m.p. 462°; b.p. 1390° C.; oxides TeO, Te0 5 
Te0 3 ; acids, H 2 Te0 3 , H 2 Te0 4 . 

Selenium and tellurium closely resemble sulphur in chemical properties 
They have crystalline and amorphous forms. The elements occur in natur 
frequently associated with sulphur. Selenium is frequently present in iroi 


THE LESS COMMON ELEMENTS 


305 


pyrites, hence is found in the flue dust of lead chambers of the sulphuric acid 
plant, and as an impurity in sulphuric acid, prepared from pyrites containing 
selenium. 

Selenium occurs in copper and iron pyrites; meteoric iron. In the rare 
minerals clausthalite, PbSe; lehrbachite, PbSe-HgSe; onofrith, HgSe-4HgS; 
eucairite, CuSe-Ag 2 Se; crookesite, (CuTlAg)Se. 

Tellurium.—Occurs in tellurides and arsenical iron pyrites. Frequently 
associated with gold, silver, lead, bismuth and iron. In the minerals—altaite, 

1 PbTe; calaverite, AuTe 2 ; coloradolite, HgTe; nagyagite, (AuPb) 2 (TeSSb) 3 ; 
petzite, Ag 3 AuTe 2 ; sylvanite, AuAgTe 4 ; telluride, Te0 2 (tellurium ochre); 
tetradymite, Bi 2 Te 3 . 

Solubility. Selenium.—Amorphous selenium is soluble in carbon disul¬ 
phide; the crystalline hexagonal form is insoluble in this reagent. The 
, metal is soluble in hydrochloric acid in the presence of nitric acid. It is 
| soluble in cold concentrated sulphuric acid, forming a green-colored liquid, 
which diluted with water deposits selenium. The dioxide, Se0 2 , is readily 
! soluble in hot water. 

Tellurium.—The element dissolves in hot concentrated hydrochloric acid. 
On dilution of the solution a precipitate of H 2 Te0 3 -Te0 2 occurs. Treated 
with concentrated nitric acid or aqua regia H 2 Te0 4 forms. With sulphuric 
acid the compound H 2 Te0 3 forms and S0 2 is evolved. The element dis¬ 
solves in concentrated potassium cyanide, from which solution concentrated 
hydrochloric acid precipitates all of the tellurium. Tellurium is insoluble 
in carbon disulphide. The oxides TeO and Te0 2 are soluble in acids, Te0 3 
is not readily soluble. All the oxides dissolve in hot potassium hydroxide 
solutions. 

Selenium and tellurium appear with the hydrogen sulphide subgroup ele¬ 
ments in the ordinary course of qualitative analysis. The acid solution of the 
material is treated cold with H 2 S, as the lemon-yellow SeS, formed in a cold 
solution is more readily soluble in alkaline sulphide solutions than the orange- 
yellow SeS 2 precipitated from hot solutions. Although only a partial separa¬ 
tion takes place the extract will contain sufficient selenium, if present in the 
sample, to give a qualitative test. By precipitation from an acid solution by 
H 2 S, selenium and tellurium are separated from members of subsequent groups. 
The sulphides precipitated are extracted with sodium or ammonium sulphide 
and the extract examined for selenium and tellurium. 







306 


QUALITATIVE ANALYSIS 


DETECTION OF SELENIUM 

General Procedure.—The sodium or ammonium extract is acidified with 
hydrochloric acid, whereby selenium together with the other members of 
the group are precipitated. The washed and dried precipitate is mixed with 
twice its weight in a flux containing equal parts of sodium carbonate and 
nitrate, and the mixture added to an equal amount of the flux which has been 
previously fused. The fluid mass is poured on to a slab of porcelain and the 
cooled melt placed in a beaker and extracted with water, whereby selenic, 
telluric, molybdic and arsenic acids dissolve, stannic oxide, sodium anti- 
monate, gold and the platinum group remaining insoluble. The extract 
is treated with an excess of hydrochloric acid and boiled to reduce 
sodium selenate, Na 2 Se 04 , to selenious acid, H 2 Se 03 . A reducing agent 
such as sulphurous acid, ammonium sulphite, hydrazine sulphate or hy- 
droxylamine is added and the solution boiled. Selenium, if present, is pre¬ 
cipitated in its red or brown colored metaflic form. The red color darkens on 
boiling. 

Selenium is an odorless and tasteless solid. Its vapor has a putrid horse-, 
radish odor. The element burns with a reddish-blue colored flame. 

Dissolved in concentrated sulphuric acid a fine green-colored solution ia 
obtained, from which solution selenium may be precipitated by diMka with 
water, the suspended substance giving a reddish tint to the acid.. 

Hydrochloric acid decomposes selenates with evolution of chlorine gas on 
boiling. 

Barium chloride precipitates white BaSeCh, soluble dilute HC1, when 
added to selenites, and white BaSe0 4 , insoluble in dilute HC1, when added to 
selenates. 

Hydrogen sulphide produces no precipitate with a selenate. This reduced, 
however, by heating with HC1, a lemon-yellow to an orange-yellow precipi¬ 
tate of SeS 2 is obtained. 

The gas passed into a solution of selenite gives an immediate precipita¬ 
tion of the sulphide, SeS 2 . 

DETECTION OF TELLURIUM 

Tellurium, dissolved in concentrated sulphuric acid: the acid purple or 
carmine. The color disappears on dilution. The mineral may be treated 
directly with hot concentrated sulphuric acid and the color obtained in presence 
of tellurium., 

Heated in a test-tube tellurium compounds sublime and fuse to colorless, 
transparent drops of Te0 2 . 

Hydrogen sulphide precipitates metallic tellurium mixed with sulphur 


THE LESS COMMON ELEMENTS 


307 


when passed into acid solutions containing the element. The precipitate 
resembles SnS in appearance. It is readily soluble in (NH 4 ) 2 S. 

Tellurium burns with a greenish flame. 

Reducing agents added to acid solutions of tellurium precipitate black 
metallic tellurium. 

Tellurium compounds are not as readily reduced as are those of selenium. 
In solutions having an acidity of over 80 per cent, S0 2 gas causes the precipita¬ 
tion of metallic selenium alone. Upon dilution with an equal volume of water 
tellurium is precipitated. A separation may be effected in this way. 

Tellurates boiled with HCl evolve chlorine gas and are reduced to H 2 Te0 3 . 
Dilution of the solution will cause the precipitation of Te0 2 (distinction from 
Se). 

Potassium iodide added to a tellurite in dilute sulphuric acid solution 
* (1:4) precipitates black Tel 4> soluble in excess of KI. 




TUNGSTEN 

W., at.wt. 184.0; sp.gr. 18.77; m.p. 3000° C.; oxides, W0 2 (brown) 3 W0 3 
(yellow); acids, H.WO^ ortho tungstic; H 2 W 4 O u , meta tungstic. 

Tungsten occurs principally as wolfram, a tungstate of iron and manganese 
(FeWO 4 • MnO 4 ), and as scheelite, a tungstate of calcium (CaW0 4 ). The best 
concentrate of hand-picked material contains 70 to 74 per cent tungsten in 
terms of its oxide, W0 3 . 

The element is met with in alloys—ferro-tungsten, silico-tungsten, tung¬ 
sten steels containing as much as 10 to 20 per cent of the metal, used for 
making high-speed, self-hardening cutting tools; tungsten powder, alkali 
tungstates for mordanting purposes; tungstic oxide, W0 3 ; tungsten electric 
light filaments, etc. 

For solution of the sample the following facts should be kept in mind 

regarding solubilities. _ __ _ . . . 

The metal is practically insoluble in HCl and in H 2 S0 4 . It is slowly 
attacked by HNO s , aqua regia and by alkalies. It is readily soluble in a 

mixture of HN0 3 and HF (=WF 6 or WOF 4 ). . 

Oxides.—'W0 2 is soluble in hot HCl and in hot H 2 S0 4 (-red sol.), also m 
KOH (red sol.). The oxide W0 3 is scarcely soluble in acids, but is readily 
soluble in KOH, K 2 C0 3 , NH 4 OH, (NH 4 )C0 3 , (NH 4 ) 2 S*. Both the acid 
and the alkali solutions deposit the blue oxide on standing. 

Acids. Ortho tungstates.—A few are soluble in water and in acids, I he 




308 


QUALITATIVE ANALYSIS 


alkali salts only slightly soluble. The meta tungstates are easily soluble in 
water. Tungstates are precipitated from alkali salts by dilute H 2 SO 4 , HC1, 
HN0 3 , H 3 PO 4 (aqua) as yellow W0 3 -H 2 0 or white W0 3 -2H 2 0. Meta 
tungstates are not precipitated by cold acids, but are precipitated by boiling 
and by long standing. 

Solution of Minerals. Fusion Method.—The material may be opened out 
by fusion with alkalies or alkaline carbonates, or by solution in mixtures of 
acids of which hydrofluoric acid is a constituent. 

Compounds of Tungsten, (a) Soluble.—Dioxydichloride, W0 2 C1 2 , yellow; 
tungstic acid (meta), H 2 W 4 O 13 , yellow. 

( 6 ) Decompose or are Insoluble.—Bromides, WBr 2 , WBr 5 , blue black to 
violet brown; chlorides, WC1 2 , WC1 4 , WC1 5 , WCl fl , steel gray to black; oxides, 
W0 2 , brown; W0 3 , yellow; Sulphides, WS 2 , dark gray, WS 3 , black (sol. 
alkalies, alk. sulphides). 


DETECTION 

Minerals.—The finely powdered material is fused with about six times its 
weight of potassium hydroxide in a silver or nickel crucible. (Fusion with 
Na 2 C0 3 or with KHS0 4 in platinum will also decompose the material.) 
The cooled mass is extracted with hot water and filtered. The solution is 
treated with about 25 cc. of dilute hydrochloric acid and boiled. The pre¬ 
cipitate formed may contain antimony, molybdenum, niobium, silica, tan¬ 
talum, tin and tungsten. This is filtered and the moist residue treated with 
a solution of yellow ammonium sulphide. Antimony, molybdenum, tin and 
tungsten pass into the filtrate, niobium and tantalum remain on the filter. 
The ammoniacal sulphide extract is acidified with hydrochloric acid and boiled. 
The precipitate is filtered and washed with a little hydrochloric and nitric 
acids. Antimony, molybdenum and tin pass into the filtrate, while tungsten 
and sulphur remain on the filter. Tungsten is now confirmed as follows, 
portions of the precipitate being taken: 

1 . The residue is suspended in dilute hydrochloric acid and a piece of zinc, 
aluminum, or tin placed in the solution. In the presence of tungsten a blue- 
colored solution or precipitate is seen, the color disappearing upon dilution 
with water. 

2. A portion of the precipitate is warmed with ammonium hydroxide and 
the extracts absorbed with strips of filter paper. 

(а) A strip of this treated paper is moistened with dilute hydrochloric acid 
and warmed. In the presence of tungstic acid a yellow coloration is produced. 

( б ) A second strip of paper is moistened with a solution of stannous 
chloride. A blue color is produced in the presence of tungsten. 


THE LESS COMMON ELEMENTS 


309 


(c) A third strip dipped into cold ammonium sulphide remains unchanged 
util warmed, when the paper turns green or blue if tungsten is present. 

Iron, Steel and Alloys. These decomposed with strong hydrochloric acid 
•llowed by nitric acid leave a yellow residue in the presence of tungsten. If 
lis residue is digested with warm ammonium hydroxide and the extract 
raporated to dryness a yellow compound, W0 3 , will remain if tungsten is 
resent. This oxide may be reduced in the reducing flame in the blue-colored 
dde. 



310 


QUALITATIVE ANALYSIS 


RARER ELEMENTS OF THE AMMONIUM SULPHIDE GROUP 

CERIUM AND THE OTHER RARE EARTHS 


Group* 

Symbol 

At. W T .t 

Sp. Gr. 

M. P. 

Oxides 

Yttrium . 

. Yt 

89.33 

3.800 

1250 

Yt 2 0 3 

Erbium. 

Er 

167.7 

4.770 


Er 2 0 3 , Er 2 0 6 

Holmium . 

. Ho 

163.5 




Thulium 

Tm 

168.5 



Tm 2 03 

Dysprosium . 

• Dy 

162.5 




Ytterbium . 

. Yb 

173.5 

. 

1800 

Yb 2 0, 

(Neo-ytterbium) 






Lutecium . 

. Lu 

175.0 




Europium . 

. Eu 

152.0 




Victorium . 


Discovery 

not confirm 

ed. 


Group 2: 






Terbium 

Tb 

159.2 



Tb 2 0, 

Gadolinium. . 

. Gd 

157.3 

1.310 


Gd 2 03 

Group 3: 






Cerium . 

. Ce 

140.25 

6.625 

950 

Ce 2 0 3 , Ce 2 O e 

Lanthanum 

La 

139.0 

6.163 


La 2 0 3 

Neodymium . 

. Nd 

144.3 

6.544 

840 

Nd 2 0 3 

Praseodymium. . . . 

. Pr 

140.9 

6.544 

940 

Pr 2 0 3 

Samarium . 

. Sa 

150.4 

7.700 

1350 

Sm 2 0 3 

Sm.nAi.um.. . 

. Sc 

44.1 


1300 

Sc 2 0 3 

Decipium . 

Discovery 

not confirm 

ed. 



♦According to Bohm (Browning, " Introduction to the Rarer Elements.”) 
t International atomic weights, 1920. 


The estimation of the rare earths is not required, other than Cerium, at 
the present time except in a few special instances as the various elements have 
found but limited commercial applications. They have all been separated 
from their native combinations, but only a few have been isolated and many 
are still believed to be combinations of elements. 

Cerium enters into the manufacture of Welsbach mantles; in the form ol 
Ce2(SC>4)3 it is used in the manufacture of aniline black; as oxalate, it is used 
in medicine, and as metal in alloys. 






































THE LESS COMMON ELEMENTS 


311 


j Yttrium is employed in the fabrication of Nernst lamp filaments and gas 
| mantles. 

The most important ores which contain the rare earth elements are: 


raw material for Ce, La. 


Yt earths. 
Yt 
Yt 
Ce 
Yt 
Yt 
Yt 
Yt 


Monazite, (Ce, La, Di, Th)*P0 4 , 

Gadolinite, Be 2 FeY 2 Si 2 0 1 0 , 

Xenotime, YtP0 4 , 

Euxenite, R'" (NbT) 3 ) 3 • R 2 '" (Ti0 3 ) 3 • 3/2H 2 0, 

Cerite, (Ca, Fe)(CeO)(Ce 2 -30H)(Si0 3 ) 3 , 

Samarskite, R 3 "R 2 ,,, (Nb, Ta) 6 0 2 i, 

Yttrotantalite, R"R 2 "'(Nb, Ta) 4 0i 5 -4H 2 0, 

| Sipylite, complex, 

Keilhauite, complex silicate, 

In the formulas given above R" stands for any dibasic radical or element 
while R"' stands for any tribasic radical or element. 

Solution. 1. Fusion Method.—The finely pulverized sample is fused with 
sodium carbonate and the melt after cooling is extracted with cold water. A 
sufficient quantity of hydrochloric acid to impart an acid reaction is added. 
The solution obtained is evaporated to dryness and baked to dehydrate the 
silica, then treated with a little hydrochloric acid and after dilution with 
water, filtered. Ammonia water is added to the solution in slight excess 

I and the solution allowed to stand until the precipitate has settled. It is 
then filtered off, washed with cold water and dissolved in hydrochloric acid. 
All of the rare earths are then present in the solution as chlorides. (Yttrium 
group with carbonate precipitate.) 

2. Acid Extraction.—Decomposition of the finely pulverized sample may 
be effected by mixing it with a sufficient quantity of sulphuric acid to make a 
paste and then heating the mass, slowly at first and then gradually increasing 
the heat to dull redness when fumes of S0 3 appear. After cooling, the mass 
is extracted with cold water and the metals of the H 2 S group removed in the 
usual way. The rare earths are then present in the solution as sulphates and 
may be separated by one of the methods detailed below. 

3. Decomposition by Means of Hydrofluoric Acid.—Samarskite and 
euxenite in the finely powdered state are moistened with their own weight 
of water and twice as much fuming hydrofluoric acid. The attack takes 
place in a few seconds. When the violent action is over the solution is evap¬ 
orated to dryness on the steam bath, taken up with water (30 to 40 cc. for a 
5-gram sample) and the contents of the dish filtered and washed. The 
mineral is then divided into two portions, the filtrate containing all the 
metallic acids, iron and manganese, the insoluble portion containing all the 
rare earths and uranic acid. 






312 


QUALITATIVE ANALYSIS 


The difficulty of attack increases in proportion to the amount of tantalic 
acid present in the sample. The rare earths are then extracted from the 
incoluble portion by one of the methods previously mentioned. Fusion with 
sodium carbonate is preferred. 

RARE EARTH GROUP SEPARATIONS 

Separation of the rare earths from iron, aluminum and thorium may be 

effected by adding sodium fluoride to the hydrochloric acid solution of the 
Iron Group which has been precipitated as hydroxide. The precipitate, which 
consists of the double fluorides of the rare earths and thorium, is washed 
thoroughly and evaporated with sulphuric acid on the sand bath to decompose 
the fluorides. This process removes the alkaline earths as insoluble sulphates. 
The excess acid is removed by fuming and the solution of the sulphates after 
diluting and warming is treated with sodium thiosulphate in solution. Tho¬ 
rium thiosulphate is precipitated. In solution are the sulphates of all the 
rare earths. 

Cerium, lanthanum, praseodymium, neodymium, europium and gado¬ 
linium may be separated from the other rare earths by adding a saturated 
solution of potassium sulphate to the sulphate or chloride solution of all of the 
rare earths. The above-mentioned elements form insoluble double salts. 

Scandium may be separated from yttrium by boiling a solution of the 
nitrates. A basic scandium nitrate is first precipitated. 

Yttrium Group.—Barium carbonate forms no precipitate in the cold, hence 
the elements comprising same may be separated from aluminum iron, chro¬ 
mium, thorium, cerium, lanthanum, praseodymium, and neodymium by this 
means. 

Yttrium Group.—The precipitation of the group as hydroxides is not 
affected by the presence of tartaric acid. Hence the members may be thus 
separated from aluminum, glucinum, thorium, zirconium, and iron. 

Praseodymium, neodymium, lanthanum, and samarium may be separated 
from each other by the fractional precipitation of a dilute solution of the 
nitrates with a very dilute solution of ammonia water (1 gram of NH 3 in 500 
cc.). The first precipitates are rich in samarium; the didymiums come down 
next and the lanthanum in the last portions. By a continual repetition nearly 
pure salts may be obtained. 

Besides the separations mentioned above the group members may be freed 
from each other by various other methods, as for example: 

(1) Fractional crystallization of the picrates. 

(2) Fractional crystallization of the double magnesium nitrates. 

(3) Fractional precipitation of the oxalates in a nitric acid solution,"etc. 


THE LESS COMMON ELEMENTS 


313 


DETECTION 

The samples having been brought into solution by one of the procedures 
outlined, the elements may be precipitated as oxalates from an ammoniacal 
solution detected by one of the following tests: 

Spectroscopic.—Many of the rare earth’s elements have either character¬ 
istic spark spectrums or absorption spectrums and their presence may be 
detected by this means. 

Yttrium, no absorption spectrum; gives brilliant spark spectrum. 


Erbium, 

gives “ 

(< 

cc 

cc 

(t 

(< 

Ytterbium, 

no 

(( 

CC 

cc 

CC 

cc 

Terbium, 

no “ 

CC 

“ 

cc 

11 

cc 

Cerium 

no “ 

CC 

CC 

cc 

Cl 

cc 

Lanthanum, 

no 

cc 

cc 

cc 

Cl 

cc 

Samarium, 

gives “ 

cc 

no 

spark spectrum. 


! Scandium, 

no “ 

cc 

cc 

CC 

cc 


Praseodymium, no 

cc 

cc 

CC 

cc 


Neodymium, 

no 

cc 

cc 

CC 

cc 



Cerium shows lines of greatest intensity in the arc spectrum at 4337.9, 
j 4527.5, 4386.9, 4594.1. In the spark spectrum at 4460.3, 4562.5, 4572.4, 
4594.1, 4628.3. All of these lines are in the visible spectrum. 

The element having been brought into solution by one of the methods 
detailed above and separated from the base metals, silica and thorium may be 
isolated from the other rare earths by precipitation in a slightly acid solution 
with oxalic acid. The precipitate is allowed to settle twenty-four hours, 
j filtered, washed with water and ignited. The oxides are then dissolved in 
hydrochloric acid and precipitated as hydroxide by the addition of an excess 
of caustic potash. The precipitate, suspended in solution, is subjected to the 
j action of chlorine gas which is bubbled through in a steady stream. All of 
| the rare earths except cerium are converted into the chlorides, while the 
latter remains as a reddish, gelatinous precipitate, ceric hydroxide — 
2Ce0 2 3H 2 0. 

In the wet way cerium may be detected when in the form of cerium nitrate 
by boiling with lead peroxide and nitric acid. A deep yellow color is imparted 
to the solution, due to the formation of ceric nitrate. 

Cerium may be detected by the addition of sodium hypochlorite to the 
solution of a colorless cerous salt. Red ceric hydroxide is precipitated. The 
test may be confirmed by the chlorine gas evolved when the precipitate is 
dissolved in hydrochloric acid. 

Cerous salts are precipitated by fixed alkalies and are insoluble in excess. 







314 


QUALITATIVE ANALYSIS 


Tartaric acid hinders the precipitation. Ammonium sulphide also precipi¬ 
tates the hydroxide. Oxalic acid precipitates cerous oxalate, white, from 
moderately acid solutions. It is soluble in hot ammonium oxalate but pre¬ 
cipitated by dilution with cold water. 

Lanthanum may be detected by adding iodine to the washed precipitate, 
formed by the addition of ammonium hydroxide to a solution of its salts. A 
characteristic blue coloration results. 

Praseodymium, neodymium, may be detected by the reddish color of their 
solutions also by the rose-red or violet color imparted to a bead of microcosmic 
salt when heated in the flame of a blow pipe. 

Scandium.—The hydrochloric acid solution of a scandium salt, when boiled 
for thirty minutes with solid Na 2 SiFl6 gives a precipitate which is free from all 
the other rare earths, the scandium taking the place of the sodium in the com¬ 
pound. 

Ytterbium may be detected by adding to a neutral solution H 2 Se 03 * 4 H 2 0 . 
A white precipitate of Yb 2 (SeC> 3 ) 3 , which is insoluble, results. 

Erbium. —In the flame test this earth gives an intense green light. 


GLUCINUM (BERYLLIUM) 

Gl, at.wt. 9.1; sp.gr. 1.85 20 °; m.p. > 960° C.; oxide, GIO. 

Glucinum occurs in the minerals beryl, euclase, davalite, chrysoberyl, 
helvite, leucophane, phencaite. 

The oxide, GIO, is soluble in strong sulphuric acid. It is decomposed by 
fusion with potassium fluoride. The freshly precipitated hydroxide, Gl(OH) 2 , 
is easily soluble in dilute acids, in alkalies and alkali carbonates and bicar¬ 
bonates. 

DETECTION 

General Procedure.—In the usual course of analysis glucinum will be 
precipitated by ammonia along with iron and aluminum hydroxides. Silica 
having been removed by evaporation to dryness of the acid solution of the 
substance, extraction of the residue with dilute hydrochloric acid and sub¬ 
sequent filtration; the members of the hydrogen sulphide group are precipi¬ 
tated from slightly acid solution by hydrogen sulphide. The filtrate is con¬ 
centrated to about 30 cc., and about 2 grams of sodium peroxide are added 
to the cooled liquid, which is now heated to boiling and filtered. Fe(OH )3 
remains insoluble, if iron is present, while aluminum and glucinum dissolve. 
The filtrate is acidified with nitric acid, and ammonia then added in excess. 


THE LESS COMMON ELEMENTS 


315 


If a precipitate forms, alumina or glucinum or both are indicated. Glucinum 
hydroxide and aluminum hydroxide cannot be distinguished by appearance; 
the solubility of the former in sodium bicarbonate solution makes it possible 
to separate the two. The precipitate is dissolved in acid and the solution 
made almost neutral with ammonia. .Solid sodium bicarbonate is added 
in sufficient amount to make the solution contain 10 per cent of the reagent 
and the mixture heated to boiling, then filtered. Alumina hydroxide remains 
on the filter paper and glucinum passes into the filtrate, in which it may be 
detected by diluting to ten volumes with water and boiling, whereupon 
glucinum hydroxide precipitates. 

Glucinum hydroxide, Gl(OH) 2 , is precipitated from neutral or acid solu¬ 
tion by ammonia, insoluble in excess (distinction from Al(OH) 3 ). It is pre¬ 
cipitated by sodium and potassium hydroxides, soluble in excess (separation 
from iron); if this solution is boiled Gl(OH )2 is reprecipitated, Al(OH) 3 
remains in solution. Gl(OH) 2 is soluble in an excess of ammonium carbonate, 
Al(OH )3 is insoluble. 


THORIUM 

Th, at.wt. 232.4; sp.gr. 7.7; 11.00; m.p. 1700°; oxides Th0 2 . 

The estimation of thorium is required chiefly in the fabrication of incan- 
I descent gas mantles. Raw materials such as monazite P0 4 (Ca, La, Di, Th) 
and thorite (ThSi0 4 ) are generally used. The former usually contains from 
2 to 4 per cent of thorium while the latter runs as high as 81.5 per cent. Tho- 
, rium nitrate in a rather impure state is the chief intermediate product. The 
| finished mantles generally contain 99 per cent Th0 2 and 1 per cent Ce0 2 . 

Solution.—“ A ” Silicates (as thorite, etc.) are decomposed by treatment 
with ten times their weight of fuming hydrochloric acid. This treatment 
usually suffices, but in cases where an insoluble residue still remains it is fused 
with ten times its weight of sodium carbonate in a large platinum crucible. 
The fusion is dissolved in hydrochloric acid and added to the solution obtained 
from the first extraction. After the silica and the metals of the first group 
are removed in the usual way the solution is freed from H 2 S by boiling. The 
thorium together with the other rare earths, calcium, magnesium, etc., are 
, then present as chlorides and the necessary separations made as detailed under 

gravimetric determination. . 

“ B ” Phosphates (as Monazite, etc.) Fusion with Potassium Acid 
Sulphate.—0.5 gram of the finely pulverized material is mixed with 10 grams of 
potassium acid sulphate in a large platinum crucible, covered and heated until 








316 


QUALITATIVE ANALYSIS 


gentle fusion takes place and no further gas is given off. Then ignite over free 
flame for a few minutes, cool and treat with a little water and hydrochloric 
acid, until complete decomposition takes place. Boil for a few minutes, 
allow to cool and settle and decant off the clear liquid. The residue is treated 
with concentrated sulphuric acid and again extracted with water. 

• DETECTION 

(1) By means of the spectroscope. Thorium shows lines of greatest 
intensity in the arc spectrum at 4863.3, and 4919.9. 

(2) (NH) 4 C0 3 precipitates white carbonate, soluble in excess. Repre¬ 
cipitated on boiling. 2 

(3) K2SO4 precipitates Th(S0 4 ) 4 Kv 2H 2 0 insol. in concentrated K 2 S0 4 
solution. 

(4) By radio activity. Thorium compounds possess the power of contin¬ 
ually emitting Becquerel rays and radio active emanations. 


TITANIUM 

Ti, at.wt. 48.1; sp.gr. 4.5°; m.p. 1795° C. (±15°); oxides TiO, Ti 2 0 3 , 

Ti0 2 , TiO 3 . 

The element is widely distributed in minerals, soils, clays and titaniferous 
iron, FeTi0 3 . It is found in granite, gneiss, mica, slate, syenitic rocks, granu¬ 
lar limestone, dolomite, quartz, feldspars and a large number of other minerals. 
The principal commercial minerals are: 

Umenite, FeTi0 3 , containing about 52.7 per cent Ti0 2 . 

Rutile, Ti0 2 , containing 90 to 100 per cent Ti0 2 . 

Titanite, CaTiSi0 6 , containing 34 to 42 per cent Ti0 2 . 

Perovskite, CaTi0 3 , containing about 60 per cent Ti0 2 and 5 to 6 per 
cent Yt 2 0 3 . 

Titaniferous ores of variable titanic oxide content. 

By far the most important application of titanium at the present time is 
the use of ferrotitanium in the iron and steel industry. 

DETECTION 

The powdered ore is fused with potassium bisulphate, KHS0 4 , until effer¬ 
vescence ceases. The cooled mass is dissolved in dilute sulphuric acid by 
boiling. Hydrogen peroxide, H 2 0 2 , added to this titanium solution, produces 
a yellow to orange color, according to the amount of titanium present. Hydro¬ 
fluoric acid, or fluorides, destroys the color. Vanadium also produces this 


THE LESS COMMON ELEMENTS 


317 


color with hydrogen peroxide, but the color is not destroyed by HF. The 
yellow color, according to Weller is due to Ti0 3 formed. 

Morphine produces a crimson color with solutions of titanium in sulphuric 

acid. 

Zinc added to hydrochloric acid solutions of titanium produces a blue color, 
tin a fine violet solution. 

If sulphur dioxide, S0 2 , is passed into the solution of titanium to reduce the 
iron, and the slightly acid solution then boiled, yellowish white metatitanic 
acid, TiO(OH) <2 , is precipitated. 

Bead Test on Charcoal.—A small portion of the powdered mineral heated 
on charcoal with microscosmic salt and tin produces a violet-colored bead if 
titanium is present, 


URANIUM 

U, at.wt. 238.5; sp.gr. 18.7; m.p. <1850° C.; oxides U0 2 , U0 3 , 
(oxide U 3 0 8> formed by ignition = U0 2 +2U0 3 ). 

The element occurs in the following minerals: 

Pitchblende, or uraninite, containing 40 to 90 per cent U 3 O g . 

Autunite, Ca(U0 2 ) 2 P 2 0 8 -8H 2 0, contains 55 to 62 per cent U0 3 . 
Torbernite, Cu(U0 2 ) 2 -P 2 0 6 -8H 2 0, contains 57 to 62 per cent U0 3 . 
Carnotite, a vanadate of potassium and uranium, V 2 05 *U 2 0 3 *K 2 0 - 3 H 2 0 . 
Samarskite, a urano-tantalate of iron and yttrium, etc., 10 to 13 per cent 

uo 3 . 

Fergusonite, a columbate of cerium, uranium, yttrium, calcium and iron. 
Nearly all the silicates, phosphates and zirconates of the rare earths contain 
uranium. 

The element is used in the ceramic industry for producing yellow, brown, 

|gray, and velvety-black tints. It produces canary-yellow glass. It is used as 
a mordant in dyeing of silk and wool. It also finds use in photography. The 
metal is used in cigarette-lighters and self-lighting burners. 

Solubility .—The element dissolves in hydrochloric and in sulphuric acids; 
less readily in nitric acid. It is insoluble in alkaline solutions. 

The oxide, U0 2 , dissolves in nitric acid and in concentrated sulphuric 

\The salts, UF 4 and U0 2 (HP0 4 ) 2 -4H 2 0, are insoluble in water, but dissolve 
in strong mineral acids. 








318 


QUALITATIVE ANALYSIS 


DETECTION 

The mineral is warmed with a slight excess of nitric acid (1 : 1) until 
decomposition is complete. The solution is diluted with water and then an 
excess of sodium carbonate added and the mixture boiled and filtered. Suffi¬ 
cient nitric acid is added to neutralize the carbonate, and after expelling the 
CO 2 by boiling, sodium hydroxide is added to the filtrate. A yellow precipi¬ 
tate is formed in presence of uranium. The precipitate is insoluble in an excess 
of the reagent, but dissolves in the ammonium carbonate. 

Uranous salts are green or blue and form green or bluish-green solutions, 
from which alkalies precipitate uranous hydroxide, reddish brown, insoluble in 
excess, but readily dissolved by ammonium carbonate. Uranous salts are 
strong reducing agents. 

Uranyl salts (U0 2 -R 2 ) are yellow. Alkali carbonates give a yellow pre¬ 
cipitate, soluble in excess. U0 2 is regarded as a basic radical, known as 
“uranyl.” The radical migrates to the cathode, upon electrolysis of a uranyl 
solution. Uranyl salts are more stable than uranous and are better known. 


VANADIUM 

V, at.wt. 61.0; sp.gr. 6.026; m.p. 1720° C.; oxides V 2 0, V 2 0 2 , V 2 0 3 , V 2 0 4 , 
V 2 0 5 ; vanadates—meta NaV0 3> ortho Na 3 V0 4 , pyro Na 4 V 2 0 7 , tetra 
Na 3 HV 6 0i 7 , hexa Na 2 H 2 V 6 0 17 . 

The materials in which the estimation of vanadium is desired may be sur¬ 
mised from the following facts: Industrial application. Vanadium is used in 
special iron and steel alloys. It increases the strength of steel as well as the 
compression power, without loss of hardness, and increases the resistance to 
abrasion; hence vanadium steels are used in locomotive and automobile 
cylinders, pistons, bushings and in all parts of machines subject to jar. It 
is used in high-speed tools, vanadium bronzes for gears, trolley wheels, etc. 
It is used in indelible inks, and in the form of alkali vanadates and hypo- 
vanadates it serves as a mordant for aniline black on silk, for calico printing 
and like uses. Vanadium salts are used in ceramics where a golden glaze is 
desired. 

The element occurs widely distributed in minute quantities. It is found in 
iron ores, hence occurs in blast-furnace slags as the oxide, V 2 0 6 . The principal 
ores are: 

Patronite , a sulphide of vanadium containing 28 to 34 per cent V 2 0 6 , 
associated with pyrites and carbonaceous matter; the principal source of 
vanadium. 


THE LESS COMMON ELEMENTS 


319 


Vanadinite, (PbCl)Pb 4 (V0 4 ) 3 , containing 8 to 21 per cent V 2 0 5 . 

Camolite , K 2 0-2U0 2 - V 2 0 5 -3H 2 0, contains 19 to 20 per cent V 2 0 5 . 
Descloizite, (PbZn) 2 NV0 5 , contains 20 to 22 per cent V 2 0 5 . 

I Roscoelite, a vanadium mica with variable composition. 

Eusynchite, contains 17 to 24 per cent V 2 0 6 . 

Cuprodescloizite, (PbZnCu) 2 (0H)V0 4 , contains 17 to 22 per cent V 2 0 6 . 
Caldorolborthite, (CuCa) 2 (0H)V0 4 , contains 37 to 39 per cent V 2 0 4 . 
Vanadium occurs in ores of copper and lead, it is present in certain clays 
and basalts, in soda ash, phosphate soda, and in some hard coals. 

Solubility.—In decomposition of the material for analysis the following 
facts regarding the solubility of the metal, its oxides and principal salts, will 
be helpful: 

Element.—The metal is not attacked by aqueous alkalies, but is soluble by 
fusion with potassium or sodium hydroxide, and sodium carbonate containing 
potassium nitrate. It is insoluble in dilute hydrochloric and sulphuric acids.- 
It dissolves in concentrated sulphuric acid and in dilute and concentrated nitric 
acid forming blue solutions. 

Oxides.—V 2 0 2 is easily soluble in dilute acids, giving a lavender-colored 
solution. 

V 2 Os is insoluble in hydrochloric and sulphuric acids, and in alkali solutions. 
It dissolves in hydrofluoric acid, and in nitric acid. 

V 2 0 4 is easily soluble in acids, forming blue-colored solutions. It dissolves 
in alkali solutions. 

I V 2 0 5 is soluble in acids, alkali hydroxide and carbonate solutions. Insol¬ 
uble in alcohol and acetic acid. 

Salts.—Ammonium meta vanadate, NH 4 V0 3 , is slightly soluble in cold 
water, readily soluble in hot water. The presence of ammonium chloride 
renders the salt less soluble. The vanadates of lead, mercury and silver are 
difficultly soluble in water. These are dissolved, or are transposed by mineral 
acids, the vanadium going into solution; i.e., lead vanadate treated with 
sulphuric acid precipitates lead sulphate and vanadic acid passes into solution. 

• 

DETECTION 

Ammonium Sulphide or Hydrogen Sulphide passed into an ammonia cal 
[solution of vanadium precipitates brown V 2 Ss, soluble in an excess of alkali sul- 
[phide and in alkalies, forming the brownish-red thio- solution, from which the 
isulphide may be reprecipitated by acids. 

Reducing Agents.—Metallic zinc, sulphites (S0 2 ), oxalic acid, tartaric acid, 
sugar, alcohol, hydrogen, sulphide, hydrochloric acid, hydrochromic and 
hydriodic acids (KI) reduce the acid solutions of vanadates with formation 






320 QUALITATIVE ANALYSIS 

of a blue-colored liquid. (See Volumetric Methods.) Reduction is hastened 
by heating. 

Hydrogen Peroxide added to a cold acid solution of vanadium produces a 
brown color, changing to blue upon application of heat. 

Solid Ammonium Chloride added to a neutral or slightly alkaline solution 
of a vanadate precipitates the colorless, crystalline salt, NH 4 VO 3 , insoluble in 
ammonium chloride. The ammonium metavanadate ignited is decomposed, 
ammonia volatilizing and the red pentoxide of vanadium remaining as a 
residue. 

The colorless ammonium vanadate solution becomes yellow when slightly 
acidified. Acids produce a red color when added to the solid salt. 

The oxide, V <f> 0 , is distinguished from Fe<iOz by the fact that it fuses very 
readily with the heat of Bunsen burner, whereas the oxide of iron, Fe 2 0 3 , is 
infusible in the heat of a blast lamp. M.p. Vs06 = 658° C.; m.p. Fe 20 3 = 
1548° C. 

Comparison of Vanadium and Chromium Salts.—Vanadium, like Chro¬ 
mium, forms a soluble salt upon fusion with sodium carbonate and potassium 
nitrate or with sodium peroxide. The solution of vanadates and of chromates 
are yellow or orange; the color of the chromate becomes more intense when 
strongly acidified, whereas that of the vanadate is reduced. The yellow color 
of the vanadate solution is destroyed by boiling with an excess of alkali, but 
may be restored by neutralizing the alkali with acid. The chromate color 
is not destroyed. (Yellow with alkalies, orange in acid solution.) Silver 
nitrate produces a dark-maroon precipitate with a soluble chromate and an 
orange-colored precipitate with a vanadate; mercurous nitrate produces a 
red-colored precipitate with chromates and a yellow with vanadates. Vana¬ 
dates are also distinguished from chromates by the reduction test; reducing agents 
such as a soluble sulphite, or sulphurous acid added to acid solutions, form a 
blue-colored liquid with vanadates and a green color urith chromates. Ammonium 
hydroxide added in excess to the cold reduced solutions gives a brown color, 
or a brown to dirty green precipitate with vanadium , and violet or lavender 
color or a light green-colored precipitate with chromium, depending upon the 
concentration of the solutions. Hydrogen peroxide Ridded to the reduced cold 
acid solutions changes the vanadium blue to reddish brown; the chromium 
green remains unchanged. 

Detection of Vanadium in Steel.—Five grams of the sample are dissolved 
in dilute nitric acid, the nitrous fumes boiled off, the solution cooled, and an 
excess of sodium bismuthate added. After filtering through an asbestos filter 
an excess of concentrated ferrous sulphate solution is added, and the solution 
divided into two equal parts in test tubes. To one portion 10 cc. of hydrogen 
peroxide are added and to the other 10 cc. of water. If vanadium is present 


THE LESS COMMON ELEMENTS 


321 


le peroxide solution will show a deeper color than the untreated solution, 
deep red color is produced with high vanadium steels and a brownish-red 
ith low. Since titanium also causes this color, it would interfere, if it were 
3 t for the fact that the color produced with titanium is destroyed by hydro- 
ioric acid and fluorides, whereas that of vanadium is not. In presence of 
tanium, 5 cc. of hydrofluoric acid are added to the treated sample. 

The brown color produced by hydrogen peroxide, with vanadium solutions, 
ill remain in the water portion when shaken with ether. The ether layer is 
>lored a transient blue in presence of chromium. 

Reduction with zinc is rapid with vanadates, much less vigorous with 
iromates. V 2 0 5 reduced to V 2 0 2 , color changes to blue, green, lavender and 
lally violet. S0 2 or H 2 S reduces V 2 0 5 to V 2 0«. V 2 0 2 forms vanadyl salts. 


ZIRCONIUM 

Zr, at.wt. 90.6; sp.gr. 4.16; m.p. 1700°±C.; oxides Zr0 2 , Zr0 3 . 

The determination of zirconium is required in minerals, artificial gems, 
candescent gaslight mantles, firebrick, enamels, glass and various salts of the 
ineral acids. The chief source of zirconium is the mineral zircon (ZrSi0 4 ) 
id its valuable modifications as hyacinth. Zircon contains from 60 to 67 
;r cent of Zr0 2 . 

Solution of Sample: 

A. Materials Containing a Large Amount of Silica 

Decomposition by Hydrofluoric Acid.—Five grams of the finely powdered 
mple are treated in a large platinum dish with 50 cc. HFand 50 cc. of H 2 S0 4 . 
hen the violent action has ceased the solution is evaporated first on the steam 
ith to expel the HF and then on a sand bath till fumes of S0 3 are given off. 
tie residue is taken up with water. This usually effects complete solution 
the sample. If, however, an insoluble residue still remains, it is filtered off, 
ashed with cold water, ignited in platinum, and fused with 10 parts by 
sight of potassium acid sulphate. The cooled fusion is dissolved by boiling 
ith 20 per cent HC1. All the zirconium will now be in solution. 

B. General Method for Minerals, Oxides, etc. 

Decomposition by Fusion with an Alkali Carbonate.—Two grams of the 
lely pulverized sample are fused with 10 grams of Na 2 C0 3 (free of sulphur) 
id 5 gram of KN0 3 in a large platinum dish. The melt is taken up in water 
id if manganese is present a few drops of alcohol are added to reduce the 







322 


QUALITATIVE ANALYSIS 


manganate to the manganous condition. The solution is filtered and th< 
residue washed with dilute NaOH solution. The filtrate then contains all th< 
silica as sodium silicate, while the residue contains all the zirconium, barium 
etc. 

DETECTION 

The zirconium having been brought into solution by one of the method; 
outlined may be distinguished: 

(1) By the addition of sodium phosphate to a slightly acid solution. A. 
white precipitate which is difficultly soluble in hydrochloric acid is character 
istic of zirconium. 

(2) By its solution in hydrochloric acid coloring turmeric paper orange 
Titanium, however, colors it brown, and is apt to mask the color due t< 
zirconium when both are present, hence it is necessary to reduce the titaniun 
by the addition of a few pieces of zinc. Reduced titanium does not colo: 
turmeric paper, but it oxidizes rapidly, hence the test should be made a: 
quickly as possible. Boric acid also produces a yellow color with turmerit 
paper, but both elements are met with in the same sample on very rare occa 
sions only. 

(3) From alumina by the solubility of its carbonate in an excess of an alkal 
carbonate. The solution from ammonium carbonate if boiled precipitate 
zirconia. 

(4) From glucinum by the insolubility of its hydroxide in ammoniun 
chloride. Glucinum hydroxide dissolves readily in the reagent. 

(5) By spectroscopic methods. Zirconium shows lines of greatest intensity 
in the arc spectrum at 4687.9, 4739.6, 4772.5, 4815.8. and in the spark spectrun 
at 3999.1, 4149.4, 4209.4, 4380.1. 

THE RARE METALS OF THE ALKALI GROUP 

Caesium, Cs, at.wt. 132.81; sp.gr. 1.87; m.p. 26.37°; b.p. 670° C.; oxide; 

CS2O, CS2O2, CS2O3, CS2O4. 

Lithium, Li, at.wt. 6.94; sp.gr. 0.534; m.p. 186°; b.p. >1400° C.; oxide Li 2 0 
Rubidium. Rb, at.wt. 85.45; sp.gr. 1.532; m.p. 38.5; b.p. 696° C.; oxide 
Rb 2 0, Rb 2 0 2 , Rb 2 0 3 , Rb204. 

Lithium occurs widely distributed, but in small quantities. Caesiun 
and Rubidium occur together in small amounts rather widely distributed 
They are found in the ash of plants and in certain minerals. 

Lithium is used commonly in the form of a benzoate; bromide; carbonate 
citrate; salicylate and chloride. Rubidium and caesium as chlorides. 


THE LESS COMMON ELEMENTS 


323 


DETECTION OF LITHIUM 

Bring the sample into solution as directed under preparation of the Solu¬ 
tion for Metals, Part IV, and separate the alkali chlorides from other con¬ 
stituents according to the standard procedure for removal of preceding groups. 
Digest the dry chlorides with amyl alcohol or with a mixture of absolute 
ilcohol and ether, filter, and evaporate the filtrate to dryness. Moisten 
the residue with dilute hydrochloric acid and examine it in the spectroscope. 
4 bright red band and a faint orange line make up the flame spectrum of 
ithium. These lie between the sodium line and the red potassium line and 
ire easily recognized 

Lithium salts impart a carmine-red color to the flame, which is obscured by 
sodium, and by large amounts of potassium. But by the proper use of a color 
screen, the lithium flame may be recognized in the presence of large amounts 
)f sodium. 

Confirmation of the presence of lithium may be had by the formation of the 
sparingly soluble lithium phosphate or lithium fluoride. 

Wet Tests .—Carbonates and phosphates of sodium or potassium precipitate, 
n solutions containing NaOH, lithium carbonate or phosphate. The salts 
ire soluble in ammonium salts. 

! DETECTION OF RUBIDIUM AND CAESIUM 

In the usual course of analysis, these rare elements are separated along with 
odium, potassium, and lithium from all other bases. In order to detect 
ubidium and caesium, extract the dry chlorides of the alkali metals with a 
ew drops of hydrochloric acid and 90 per cent alcohol. This will dissolve 
nost of the rare alkalies along with some sodium and potassium. Evaporate 
he solution to dryness, dissolve in a very small amount of water, and add 
hloroplatinic acid solution. Rubidium, caesium, and potassium chloro- 
datinates will be precipitated. Filter and wash the residue repeatedly with 
iot water to remove the potassium salt, which is much more soluble than 
ubidium and caesium chloroplatinates. During this treatment, examine 
he residue from time to time in the spectroscope. As the rubidium and 
iaesium salts are concentrated through washing, their spectra will gradually 
>ecome visible. 

Caesium and Rubidium are best studied by means of the spectroscope. 

gives orange-yellow and blue lines. Rb gives a and b lines in blue and 
lines in red, yellow, and green. 

SnCl 4 precipitates 2CsClSnCh from cone, solutions of Cs salts. HC 4 H 6 0fl 
>recipitates from cone, solutions of Rb salts white RbC 4 Ha06. 






324 


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326 


QUALITATIVE ANALYSIS 


Reagents in Solution 


Acids 



Sp. Gr. 

Concentra¬ 
tion, %. 

Approximati 
N ORM ALITY 

Factor. 

Inorganic 




Hydrochloric, saturated HC1 

1.20 

39.11 

12.9N* 

Hydrochloric, concentrated HC1 

1.12 

24.00 

8.ON 

Hydrochloric, dilute HC1 

1.03 

7.15 

2.0 N 

Nitric acid, fuming HN0 3 

1.42 

69.80 

15.7N 

Nitric acid, concentrated HNO3 

1.20 

32.05 

8.ON 

Nitric acid, dilute HNO3 

1.07 

12.30 

2.ON 

Sulphuric acid, concentrated H 2 SO/ 

1.84 

95.60 

36.ON 

Sulphuric acid, dilute H2SO4 
Sulphurous acid, saturated solution 

1.12 

17.00 

4.0 N 

of SO 2 in water 

— 

• 

3.0 N 

Organic 




Acetic acid, glacial 

1.058 

99.0 

17.6N 

Acetic acid, dilute 

1.030 

22.0 

4.ON 

Tartaric acid, 150 gm. per liter 

— 

— 

2.ON 

Alkalies 




Ammonium hydroxide, NH 4 OH 
Ammonium hydroxide, dilute 

0.90 

28.33% NH 3 

15.ON 

NH4OH 

Potassium hydroxide, KOH, 281 

0.97 

7.05% NH 3 

4.ON 

gm. per liter 

Sodium hydroxide, NaOH, 178 gm. 



4.ON 

per liter 

— 


4.ON 


* A normal solution of a reagent contains in a liter that proportion of its molecult 
weight in grams which corresponds to one gram of available hydrogen or its equivalen 
N-HC1 contains its molecular weight (36.47 g.) HC1 per liter of solution. N-H2S04 contaii 
one-half of its molecular weight, i.e., 98.08-5-2 =49.04 g., H 2 SO 4 per liter of solution. 


















REAGENTS 


327 


Salts 



Grams per Liter. 

Approximate 

Normality. 

♦Ammonium acetate, NH4C2H3O2 

308 

4 N 

♦Ammonium carbonate, (NH 4 ) 2 C0 3 

78 

add 40 cc. NH 4 OH 

2 N 

Ammonium chloride, NH 4 C1 

107.1 

2 N 

♦Ammonium molybdate, (Nfi 4 ) 2 Mo0 4 

98 

N 

Ammonium oxalate, (NH 4 ) 2 C 2 0 4 

saturated 

N 

Ammonium sulphate, (NH 4 ) 2 S0 4 

66 

N 

Ammonium sulphide, (NH 4 ) 2 S 

— 

4 N 

♦Ammonium polysulphide, (NH 4 ) 2 S X 

— 

— 

Ammonium tartrate, (NH 4 ) 2 C4H 4 0 6 

(NH4OH + 

h 2 c 4 h 4 o 6 

— 

Barium carbonate, BaC0 3 

solid diff. in H 2 0 

_ 

Barium chloride, BaCl 2 *2H 2 0 

122.2 

N 

Barium hydroxide, Ba(OH) 2 

sat. sol. 

i N 

Calcium chloride, CaCl 2 ' 

55.6 

N 

Calcium hydroxide, Ca(OH) 2 

sat. sol. 

it N 

Calcium sulphate, CaS0 4 

sat. sol. 

■ is N 

Cobalt nitrate, Co(N0 3 ) 2 . 6H 2 0 

62.3 

h N 

Ferric chloride, FeCl 3 -6 H 2 0 

91 

(add 5 cc. HC1) 

N 

♦Ferrous sulphate, FeS04-7 H 2 0 

139 

(add 20 cc. H 2 S0 4 
+50 gm. (NH 4 ) 2 
SO 4 ) 

N 

Lead acetate, Pb(C 2 H 3 0 2 ) 2 -3 H 2 0 

185.5 

(add HC 2 H 3 0 2 
till acid) 

N 

^Magnesia mixture 

— 

N 

j Mercuric chloride, HgCl 2 , 

sat. sol. 

h N 

Platinic chloride, H 2 PtCl6 

10.66 

A N Pt 

Potassium bromide, KBr 

59.6 

h N 

Potassium chromate, K 2 Cr0 4 

97.3 

N 


* See “ Preparation of Special Reagents.” 











328 


QUALITATIVE ANALYSIS 


Salts 



Grams per Liter. 

Approximate 

Normality. 

— 

Potassium cyanide, KCN 

65.2 

N 

Potassium dichromate, K 2 Cr 2 C >7 

73.8 

N 

Potassium ferricyanide, K 3 Fe(CN)6 

11.0 

iV N 

Potassium ferrocyanide, K 4 Fe(CN)6 

10.6 

1*0 N 

Potassium iodide, KI 

83.1 

h N 

Potassium nitrite, KN0 2 

sat. sol. 

24 N 

Potassium permanganate, KMnO 

15.8 

h N 

Potassium sulphate, K 2 S0 4 

174 

N 

Potassium thiocyanate, KSCN 

48.6 

h N 

Silver nitrate, AgN0 3 

42.5 

1 N 

Silver sulphate, Ag 2 S0 4 

sat. sol. 

-A N 

Sodium acetate, NaC 2 H 3 0 2 

^ 328 

4 N 

*Sodium carbonate, Na 2 C0 3 , fused 

212 

4 N 

Sodium chloride, NaCl 

29.3 

h N 

*Sodium cobalt nitrite, Co(N0 2 ) 3 -3 NaN0 2 

— 

—• 

Sodium phosphate, Na 2 HP0 4 -12 H 2 0 

119 

N 

*Stannous chloride, SnCl 2 cone, and dil. 

— 

— 

Zinc sulphate, ZnS0 4 -7 H 2 0 

140 

— 


* See “ Preparation of Special Reagents.” 


Other Solutions.—Amyl alcohol, C 5 HnOH; bromine water, Br; chlorine 
water, Cl; carbon disulphate, CS 2 ; ethyl alcohol, C 2 H 5 OH; indigo, 2(C 8 H 5 ON); 
hydrogen peroxide, H 2 0 2 , 3 per cent; methyl alcohol, CH 3 OH. 

Solid Reagents 

Aluminum foil, Al. 

Ammonium nitrate, NH 4 NO 3 . 

Ammonium sulphite, (NH 4 ) 2 S0 3 -H 2 0. 

Barium hydroxide, Ba(OH) 2 -8 H 2 0. 

Borax, Na 2 B 4 O 7 -10 H 2 0. 

Calcium carbonate, CaC0 3 (marble). 

Copper foil, Cu. 

Cotton, absorbent. 

Ferrous sulphate, FeS0 4 -7 H 2 0. 

Glass wool. 











REAGENTS 


329 


Iron filings, nails, or wire. 

Lead acetate, Pb(C 2 H 3 02)2, 3 H 2 0. 

Lead dioxide, Pb0 2 . 

Oxalic acid, H 2 C 2 0 4 -2 H 2 0. 

Potassium carbonate, K 2 C0 3 . 

Potassium chlorates, KC10 3 . 

Potassium cyanide, KCN. 

Silver nitrate, AgN0 3 . 

Sodium ammonium phosphate, NaNH 4 HP0 4 -4 H 2 0. 

Sodium carbonate, Na 2 C0 3 . 

Sodium and potassium nitrate, Na 2 C0 3 +KN0 3 . 

Sodium hydroxide, NaOH. 

Sodium sulphite, Na 2 S0 3 -7 H 2 0. 

Tartaric acid, H 2 C 4 H 4 06. 

Tin foil, zinc foil, and granulated tin and zinc. 

Preparation of Special Reagents 

Ammonium acetate may be prepared by neutralizing 100 cc. acetic acid 
with NH 4 OH (about 96 cc.). 

Ammonium Carbonate.—Dissolve in 80 cc. NH 4 OH(0.90)+500 cc. H 2 0, 
and dilute to one liter. 

Ammonium Molybdate.—Dilute 150 cc. NH 4 OH to 300 cc., add 72 g. 
molybdic oxide; pour slowly into solution of dilute nitric acid (250 cc. HN0 3 , 
sp.gr. 1.42 to 500 cc. water). Allow to stand several days in warm place, 
and decant clear supernatant liquid for use, diluting to one liter. 

Ammonium Sulphide.—Saturate 150 cc. strong NH 4 OH with H 2 S, add 150 
cc. NH 4 OH, and dilute to one liter. 

Ammonium Polysulphide.—Add to a portion of the above a little free 

sulphur. 

Bromine Water.—To 50 g. KBr dissolved in 500 cc. H 2 0, add 10 cc. Br. 
Shake until dissolved. 

Chlorine Water.—Saturate water with Cl gas. Keep in dark bottle. 

Cleaning Mixture.—Dissolve 50 g. of powdered K 2 Cr 2 0 7 in about 200 cc. of 
warm water; cool. Pour into cool solution with constant stirring about 250 
cc. H 2 S0 4 (cone.). 

Ferrous Sulphate.—Oxidation may be prevented by adding iron wire or 
nails to solution. 

Indigo Solution.— Dissolve in fuming H 2 S0 4 , keeping cold, 1 part indigo, 
powdered, to 5 parts acid. Allow to stand several days, then pour into 20 
parts of water. 




330 


QUALITATIVE ANALYSIS 


Magnesia Mixture—50 g. MgS0 4 and 75 g. NH 4 C1 dissolved separately 
in water; mix and add 300 cc. strong NH 4 OH. Dilute to one liter. 

Nessler’s Reagent—Dissolve 20 g. of KI in 50 cc. of water; add 32 g. Hgl. 
Dilute to 200 cc., and add 134 g. of KOH that has been dissolved in 260 cc. 
of water. 

Phenolsulphonic Acid.—Dissolve about 24 g. phenol in 150 cc. H 2 S0 4 cone., 
add 15 cc. of water. Keep in dark glass bottle. 

Sodium Cobaltic Nitrite.—Dissolve 100 g. NaN0 2 in 300 cc. H 2 0; add 
acetic acid to acid reaction, and then 10 g. Co (NO 3 ) 2 . Allow to stand several 
hours and filter. Solution will decompose. 

Stannous Chloride.—Dissolve 225 g. of SnCl 2 in 500 cc. NH 4 C1; dilute 
to one liter. Place some fragments of metallic tin in the bottle containing the 
solution. 

Starch paste may be preserved by addition of a few drops of chloroform. 


INDEX 


PAGE 

Acetic acid. 207-209 

detection of. 209 

properties of. 207 

solubilities. 264 

tabulated tests of. 260 

test for nitrite. 159 

Acidity test of free acid in solution. 63 

Acids.154- 210 

classification of. 154 

general characteristics. 154 

solubility of salts, rules for. 232 

solution, preparation of. 233 

systematic examination of. 232 

table of general tests. 235 

table of separations. 234 

Alcohol flame tests for borate. 193 

Alizarine S test for aluminum. 82 

Alkali group.140-153 

description of members of. 140 

separation of members. 149 

rare metals of. 322 

Alkaline earth group.125-139 

description of members. 125 

removal from alkalies. 152 

separations. 134 

Alloys, analysis of. 226-229 

aqua regia solution of. 328 

list of. . . .. ^28 

nitric acid solution of. 326 

• ei 

Aluminum.* • • • ° 

compounds of. 364 

detection of.®2, 92, 246 

Q 1 

properties of. 

reactions with reagents.^2, 346 

separations from other elements.109-123 

tests for (see detection). 

Alpha benzildioxime test for nickel. ^ 


331 













































332 


INDEX 


PAGE 

Ammonia, detection and properties. .....143, 151 


solubility in water. 4 

Ammonium acetate reagent, prep, of. 329 

carbonate group, properties of. 125 

reactions. 129 

tabulated tests. 250 

reactions with Al, Cr, Fe. 246 

Co, Ni, Mn, Zn. 348 

Ba, Ca, Sr. 250 

reagent. 329 

hydroxide, reactions with aluminum. 246 

antimony. 244 

bismuth. 242 

cadmium. 242 


\ 


chromium. 

cobalt. 

copper. 

lead. 

manganese. 

magnesium. 

mercury. 

nickel. 

iron. 

silver. 

separation of Al, Cr, Fe, from Co, 

and Zn. 

tin. 

zinc. 


. 246 

. 248 

. 242 

. 240 

. 248 

. 250 

_240, 242 

. 248 

. 246 

. 240 

Mn, Ni 

_120, 121 

. 245 

. 248 


See also lab. exercises under groups on metals. 


molybdate, reagent. 

test for arsenic.. 

test for phosphate.. 

polysulphide, reagent. 

solution of H 2 S group. 

see reactions and separations. 

test for cyanide. 

sulphate, tests for Ba, Ca, Sr. 

See ammonium carbonate group. 

sulphide group, descriptive. 

rare elements of.. . . # .. 

separation of members. 

tabulated tests of. 

reactions with Al, Cr, Fe. 

Co, Ni, Mn, Zn. . . 

See exercise on elements. 

prep, of reagent.. 

sulphocyanate, detection of cobalt. 

tabulated tests of.. 

Amphoteric electrolyte, definition of. 

Aniline sulphate, test for chlorate. 


. 329 

.52,53 

. 196 

. 329 

.60, 61 

.56-67 

. 179 

135, 137, 250 

. 81 

. 310 

.109-119 

. 246 

. 246 

. 248 


329 

85 

252 

3 

203 


















































INDEX 


333 


Antimonic salts, distinction from -ous. 
Antimonous salts, distinction from -io. 

reactions. 

Antimony, compounds of.. 

detection of. 

distinction from arsenic. . . 

property of. 

reactions. 

separations. 

tabulated reactions. 

Apparatus, cleaning of. 

Aqua regia, solution of alloys. 

solution of substances.... 
Arsenate, distinction from arsenite. . . , 

Arsenic acid. 

compounds of. 

detection of. 

distinction from antimony 

properties. 

reactions. 

tabulated tests. 

Arsenite, distinction from arsenate... 

Arsenous acid, detection of. 

properties of. 

tabulated tests of. 

Asbestos filter. 

Atomic weights, table of. .. 


PAGE 

. 50 

. 50 

. 69 

. 266 

.49,69 

. 50 

. 49 

_69,244 

.74-77 

. 244 

. 23 

. 228 

. 223 

. 52 

. 184 

. 267 

. .. .51, 192 

. 50 

. 51 

68, 244,254 
...244, 254 

_52, 192 

. 192 

. 184 

. 254 

. 22 

. 26? 


Barium acetate detection of chromium. 

carbonate reaction with Al, Cr, Fe. 

Co, Ni, Mn, Zn. 

chloride group. 

table of analysis. 

test for borate. 

test for chromate. 

test for fluoride. 

test for phosphate. 

test for sulphate. 

compounds of. 

detection of. 

properties of. 

reactions. 

separations. 

tabulated tests. 

Baryta test for magnesium. 

Basic acetate, method for separations of (NH^S group metals. 

Benzidine acetate, test for gold. 

Benzoic acid, tabulated tests for.. 

Beryllium. See glucinum. 

Bettendorff, test for arsenic. 


155, 


126, 


129, 


83 

246 

248 

184 

198 

193 

195 

195 

196 

197 
268 
129 
125 
250 
134 
250 
142 
122 
294 
260 

54 

























































334 


INDEX 


Bismuth, compounds of. 

detection of. 

properties of. 

reactions with. 

separations... 

Bisulphite, tests for. 

Black filter paper, test for fluoride. 

Blowpipe tests. 

test for arsenic. 

bismuth. 

cadmium. 

Borax bead tests. 

test for borate. 

Cr, Fe. 

Co, Ni, Mn, Zn. 

cobalt. 

nickel. 

Boric acid, detection of. 

properties of. 

tabulated tests of. 

Boron compounds. 

Bromate, detection of. 

Bromide compounds detection. See bromine. 

Bromine, detection of. 

properties of. 

reactions with reagents. 

solubility. 

water, preparation of. 

Buchner funnel. 


PAGE 

. 269 

.46, 242 

. 45 

.57, 242 

. 60 

...168a, 1686 

. 188 

.16, 216 

. 52 

. 46 

. 47 

.19, 218 

. 185 

. 246 

85, 88, 89, 248 

. 103 

. 106 

.185,193 

.. 184 

. 254 

... 269 

. 173 

.173,177 

. 172 

. 177 

. 269 

. 329 

. 21 


Cadmium, compounds of. 269 

detection of.47, 242 

properties of. 47 

reactions with reagents.59, 242 

separations. 

tabulated tests. 242 

Calcium chloride reactions with acids.254-261 

test for fluoride. 195 

compounds of. 270 

detection of.127, 250 

reactions with reagents. 131, 250 

separations. 134 

sulphate test for barium. 126 

oxalate. 209 

tabulated tests. 250 

Carbolic acid, tabulated tests for. 260 

Carbonate, tests for. 164 

distinction from bicarbonate. 158 

Carbon, compounds of. 271 

detection of. 157 



















































INDEX 


335 


Carbon, properties of. 

dioxide, detection of. 

solubility in water. 

disulphide, test for bromide. 

Carbonic acid, tabulated tests of. 

Carbon monoxide, detection of. 

Casserole. 

Derium and the rare earths. 

compounds of.. 

detection of. 

properties ot. 

solution of compounds of. 

Charcoal tests:. 

Chemical equilibrium. 

reactions. See group. 

Chlorate, test for. 

Chloric acid, detection of.. 

tabulated reactions. 

Chloride, detection in presence of other halogens.... 
separations. Se chlorine. 

Chlorine, detection of.. 

free, detection of. 

in presence of cyanate, cyanide, thiocyanate 

properties of. 

test for bromide. 

test for iodide. 

water, reagent. 

'hloroplatinic acid, test for ammonium. 

Chlorite, test for. 

Jhromate action on antimonious salt. 

test for barium. 

lead. 

!hromic acid and chromate, detection of. 

properties of. 

tabulated tests of. 

hydroxide. 

'hromium,compounds of. 

detection and properties. 

reactions. 

separations. 

tabulated tests. 

itric acid, tests for. 

lass-room reviews. See close of groups. 

leaning apparatus. 

mixture. 

obalt, compounds of. 

detection of. 

nitrate test for aluminum. 

ammonium and potassium. . . 
zinc. 


PAGE 

. 157 

. 158 

. 4 

. r _ 173 

. 254 

. 158 

. 22 

. 310 

.271 

. 313 

. 310 

. 311 

. 216 

. 9 

. 171 

200, 203, 255 
. 255 

.171,181 

.. 171 

.171,176 

. 171 

.. 170 

. 177 

. 177 

. 329 

. 147 

. 159 

. 50 

.126,129 

.34, 37,41, 162 

. 194 

. 185 

. 255 

. 185 

. 272 

. 83 

. 94 

. 109 

.'_ 246 

. 260 

. 23 

. 329 

. 272 

.85,248 

. 93 

. 147 

.91,108 






















































336 


INDEX 


Cobalt, properties of. 

reactions with reagents. 

separations. 

tabulated tests. 

test for ammonium. 

test for nitrite. 

Color indications of elements by H 2 S ppt. . 

reactions. 

Combustion tube tests. 

Common ion effect. 

Complex ion, definition of. 

Cone, platinum for filtering. 

Confirmatory tests for aluminum. 

chromium. 

cobalt. 

iron. 

lead. 

manganese. 

mercury. 

nickel. 

zinc. 

Copper, compounds of. 

detection of. 

group. 

properties of. 

reactions with reagents. 

separations. 

sulphate reactions with As, Sb, Sn, 

tabulated tests.. 

Crystalline, definition of. 

Curdy, definition of. 

Cyanide, tests for. 


PAGE 

... 84 

101,248 
... 109 
... 248 
... 147 
... 166 
... 64 

8 

... 213 
... 12 
8 

... 21 
... 93 

... 96 

... 103 
... 100 
.. . 34 

... 104 
... 35 

... 106 
... 108 
... 273 
.47, 242 
... 45 

... 47 

. 58, 242 
.. . 60 
244,245 
... 242 
2 
2 

164, 178 


Decantation, definition of. 2 

Definitions and chemical terms. 1 


Dichromate test for chloride. 



tests. See chromate. 



Dicyandiamidine sulphate test for cobalt.. . 



Digestion, definition of. 



Dimethylglyoxime test for nickel. 



Diphenylamine test for nitrate. 

Diphenylcarbazide test for chromium. 



Dry tests. 



Earths, rare. See cerium. 

• 


Electrolysis, definition of. c 

Electromotive series. 



Elements, list of. 263 

Equation, definition of. c 

Erlenmeyer flask. 

































































INDEX 


337 


PAGE 

Etching, test for fluoride.187, 195 

Ether, test for chromium. 84 

Evaporation, directions regarding. 22 

Ferric chloride, test for cyanide. 179 

ferrocyanide. 179 

phosphate. 196 

salicylate. 209 

thiocyanate. 180 

ferrocyanide test for sulphate. 168 

iron, distinction from ferrous. 87 

reactions with. 100 

reduction of. 101 

Ferricyanide, detection of.180, 181, 235 

reaction with ferrous iron. 99 

reactions with Al, Cr, Fe. 247 

Co, Ni, Mn, Zn. 249 

Ferrocyanide, detection of.179, 181, 235 

reactions with Al, Cr, Fe,. 247 

Co, Ni, Mn, Zn. 249 

test for iron. 87 

Ferrous iron, oxidation of. 99 

preparation of solution of. 98 

reactions with. 98 

sulphate, reagent. 329 

' test for ferricyanide. 180 

test for nitrate. 203 

test for platinum. 296 

Film tests. 13 

Filter, folding of. 22 

stand. 21 

Filtering, directions regarding. 21 

Filtrate, definition of. 2 

Filtration, directions regarding. 20 

Flame, color tests. 19 


oxidizing. 

reducing. 

structure of. 

tests, ammonium carbonate group 


for arsenic. 52 

Ba, Ca, Sr.. 250 

barium. 126 

borate. 134 

calcium. 127 

copper.*. 48 

general. 217 

Li, K, .. 253 

potassium. 144 

sodium. 145 

strontium. 128 
























































338 INDEX 

PAGE 

Fleitmann test for arsenic. 

Flocculent, definition of. 21 

Fluoride, detection of. 1951 

method for detecting silicate. 161 

Fluorine. 2 ^1 

detection of.187, 195 

properties. ^ 

reactions with salts of. 195 I 

Fluosilicates, insoluble. 188 a 

Fluosilicic acid, test for barium. 126 

Formaldehyde test for bismuth. 46 

Formic acid, properties. 275 

tabulated tests. 260 

test for platinum. 296 

Free nitric acid, detection of. 205 

sulphuric acid, detection of. 191 

Fundamental principles of analysis... 4 

Funnels, directions regarding. 21 

Fusions, methods for refractory materials. 224 

Fusion test for manganese. 104 

Gallic acid, tests for. 261 

Gatehouse test for arsenic. 54 

General procedures for detection. See element. 

Glucinum, compounds of. 275 

detection and properties. 314 

Gold, compounds of.267, 276 

detection and properties of. 293 

separation from H 2 S, group B. 75 

tabulated reactions. 245 

Gooch crucible. 21 

Granular, definition of. 2 

Groups, outline for separation of. 31 

reactions with. 28 

Gutzeit test for arsenic.52, 53 

Halogens, detection and separation of. 182 

Hanging drop test for fluoride. 188 

Heating substances. v . 16 

Hydrazine, properties. 276 

Hydriodic acid, detection of.174, 177 

properties of.173, 276 

tabulated tests for. 255 

Hydrobromic acid, detection of...173, 177 

properties of.172, 276 

tabulated tests for. 255 

Hydrochloric acid, detection of. 171 , 176 , 256 

precipitation of Ag, Hg, Pb with. 33 

procedure for dissolving solids. 222 

properties of. 170, 276 

















































INDEX 


339 


Hydrochloric acid, solubility in water. 

tabulated tests for. 

test for HC1 group. 

lead. 

. 

iron. 

mercury. 

silver. 

Hydrocyanic acid, detection of.. 

properties of. 

tabulated tests for. 

Hydroferricyanic acid, detection of. 

See also ferricyanide, 

properties of. 

tabulated tests for. 

Hydroferrocyanic acid, detection of. 

See also ferrocyanide. 

properties of. 

tabulated tests for. 

Hydrofluoric acid, detection. See fluorine. 

method for refractory substances.. 

properties. 

tabulated tests for. 

Hydrofluosilicic acid, tabulated tests. 

Hydrogen, property. 

solubility in water. 

chloride group, characteristics. 

reactions of group. 

separation of members. 

tabulated tests of.t. 

peroxide, test for chromium. 

test for nitrate. 

sulphide group, characteristics. 

detection of members. 

separations.. 

rare metals of. 

detection of. 

occurrence. 

properties. 

reactions with Ag, Hg, Pb. 

Bi,Cd,Cu,Hg+ + 

As, Sb. 

Sn, Pt, Au. 

Fe. 

Co, Ni, Mn, Zn. . . 

test for antimony. 

arsenic. 

copper. 

lead. 

mercury. 

platinum. 


PAGE 

. 4 

.'. 256 

.28, 31, 33-44 

.24, 37, 40 

. 87 

.35,37, 40 

.36, 38, 40 

. 178 

.174, 276 

. 256 

. 180 

. 175 

. 256 

. 179 

. 175 

. 256 

. 223 

. 276 

. 256 

. 276 

.. 276 

. 4 

. 33 

_37-39,240 

. 40 

. 240 

.84,194 

. 206 

. 45 

.46-79 

. 60 

. 293 

. 163 

. 161 

. 162 

_34, 35, 240 

.48,242 

.. .49, 51, 244 

. 245 

. 246 

.91,248 

. 49 

. 51 

. 48 

. 34 

. 35 

. 296 





















































340 


INDEX 


Hydrogen, sulphide test for rare metals Pt. gp. 

Se, Te, Mo 


Hydrolysis, definition of. 

of antimonic salts. 

bismuth salts. 

Hydrosulphuric acid, tabulated tests. 

See also hydrogen sulphide. 

Hydroxide method for separating Al, Fe, Cr from Co, Mn, Ni, Zn 

Hydroxylamine. 

Hypochlorite, detection of. 

Hypochlorous acid, detection. 

properties. 

tabulated tests. 

Hypophosphorus acid, detection and properties. 

\ 

Ignition tube tests. 

Indigo solution, reagent. 

test for chlorite. 

hypochlorite. 

Indium. 

Inorganic acids, tables of tests for. 

compounds.*. 

Insoluble chromium compounds. 

ferrocyanide, detection of. 

H 2 S subgroup A. 

reactions. 

tabulated tests of. 

silicate, detection of. 

substances, solution of. 

Interfering substances, (NH<i) 2 S group. 

in nitrate test. 

removal of from solution. 

Interpretation of results. 

Introduction. 

Iodate, detection of. 

Iodide. See iodine. 

reduction of antimonic salt. 

Iodine, free and combined detection of. 

properties of. 

Iodic acid, properties of.. 

tabulated tests of. 

Ionization, repression of. 

Ions and ionization. 

Iridium, compounds of. 

detection and properties of. 

solution of iridium alloys. 

Iron, compounds of. 

detection of. 

properties of. 

reaction with ferrous and ferric salts. 


PAGE 

298-302 
303,306 
7 

... 50 

..46, 65 
... 257 


... 120 
... 276 
165,171 
... 159 
... 158 
... 257 
... 187 


213 

329 

159 

159 

254 

254 

264 

186 

180 


45 


56 

240 

167 

223 

115 


204 

221 


174 


. 5C 

_174,177 

_173, 27( 

. 27t 

. 25' 

. 11 

.3, 

. 27 

. 29 

. 29 

. 27 

86, 100, 24 

. 8 

. 9 























































INDEX 


341 


iron, separations. 

table of reactions with 

test for cyanide. 

ferricyanide.. . 
ferrocyanide. . 
thiocyanate.. . 


PAGE 

. 109 
. 246 
. 179 
. 180 
. 179 
. 180 


Laboratory directions. 

exercises. See group in question. 

Lactic acid. 

table of reactions. 

Lanthanum oxalate.. 

_,ead acetate, reactions with acids. 

test for aluminum. 

chromate. 

phosphate. 

sulphate. 

sulphide. 

l^ead, compounds of. 

detection of. 

oxide test for manganese. 

properties of. 

reactions with reagents. 

tabulated tests of. 

Less common elements. Part VI. 

Lime water test for ammonia. 

CO 2 . 

magnesium. 

Liquid, preliminary examination of. 

Lithium, compounds of. 

detection of. 

properties of. 

tables of tests. 

Litmus test for ammonia. 

Loop tube test. 


. 16 

.277 

.261 

.277 

..254-261 

. 84 

.. .84,195 

. 196 

. 197 

. 167 

. 277 

34, 37, 240 

. 56 

...: 33 

37, 56,240 

.240 

. 293 

. 143 

. .158,164 

. 142 

. 221 

.278 

..252, 323 

. 322 

. 252 

. 143 

..... 164 


Magnesia mixture, reagent. 330 

test for arsenic. 69 

phosphate. 196 

Magnesium, compounds of.142, 278 

detection of.142, 250 

properties of. 142 

reactions with.146, 250 

separations. 150 

Malic acid, table of tests for. 261 

Manganese, compounds of. 279 

detection of, soils, minerals, etc. 88 

properties of. 87 

reactions with reagents.103, 248 

separations. 109 




















































342 


INDEX 


PAGE 

Manganese, tables of reactions with.... 248 

Marsh test for antimony and arsenic.50, 53 

Mass action, law of. H 

Mendeleef’s Periodio table of elements. 324 

Mercuric chloride, reaction with As, Sb, Sn.244, 245 

test for iodine. 178 

mercury, reactions with... 56 

Mercurous chloride, detection of. 35 

mercury, reactions with. 37 

nitrate, test for chromium. 84 

Mercury, compounds of. 280 

detection of -us-monovalent. 35 

-ic-divalent. 56 

' properties of. 34 

metallic, recognition of. 35 

reactions with reagents.37, 56, 240, 242 

Metallic, displacement of platinum. 297 

precipitations. See Table of Reactions. 

Metals, general grouping of.26, 27 

systematic analysis of. 221 

Metaphosphoric acid, detection. 19f 

properties of. 19( 

reactions. 257 

Metasilicate. See silicic acid. 

Metastannic acid. 72 

Microcosmic salt test for silicate. 16( 

Minerals, detection of antimony in. 5( 

gold in. 29* 

Miscellaneous tests of metals. See Part V. 

Molybdenum, property, solubility, tests of. 302 

Nessler’s reagent. 33( 

test for ammonia. 142 

Neutral, neutralization, definitions of. 2 

Nickel, compounds of. 28 

detection of.89, 106, 24! 

properties of. 8: 

reactions w r ith reagents. 10 

separations. 10' 

tables of tests of. 24 

Nitrate, detect : on of...201, 20 

Nitric acid, detection of.201, 20 

properties of. 20 

solution of substances. 22 

tabulated tests of. 25 

test of salicylate. 20 

Nitrite, detection of. 16 

in water. 16 

distinction from chlorite.158, 15 

test for iodide. 17 

















































INDEX 


343 


Nitrogen, compounds of. 

detection of. 

properties of. 

solubility in water. 

Nitroso B naphthol test for cobalt. 

Nitrous acid, properties and detection. 

open-tube test for arsenic. 

tabulated tests of. 

Notes. See throughout text. 

)rganic acids, detection of. 

group. 

list of.. 

separations. 

)rthophosphoric acid, properties and detection 
)rthosilicate. See silicic acid. 

)smium, compounds of. 

detection... 

properties of. 

)smotic pressure.. 

)xalic acid, detection of. 

properties. 

test for calcium. 

platinum. 

)xidation, definition of. 

of ferrous iron. 

test for chromate. 

without blowpipe.. 

Oxidizing action of chlorate. 

agent, action on sulphide. 

flame. 

)xygen, solubility in water. 

’alladium, compounds of. 

properties and tests of. 

’erchlorate, detection of. 

^rchloric acid. 

’ermanganate, permanganic acid, detection of. 

properties of. 

test for nitrite. 

’ersulphate method for separation of halogens.. 

’henolsulphonic acid reagent. 

test for nitrate. 

’henylhydrazine acetate test for gold. 

’hosphate. See phosphoric acid. 

’hosphoric acid, properties and detection. 

removal from solution. 

tables of reactions. 

’hosphorous acid, properties and detection of. . 

tables of reactions. 


PAGE 
, 282 
. 201 
. 200 
4 

. 103 
. 159 
. 52 
. 258 


.... 210 
.... 207 
.... 156 
. . .. 210 
190,196 

. ... 282 
.... 300 
. . .. 299 
5 

115, 209 
208, 283 
. ... 127 
.... 296 

3 

... 99 

... 97 

... 18 
... 203 
... 167 
. . . 17 

4 

283,300 
... 299 
172,200 
... 283 
202,205 
202,283 
... 165 
... 182 
... 330 
... 204 
... 295 

189, 196 
... 115 
... 258 
... 190 
... 258 



















































344 


INDEX 


Phosphorus and its acids, descriptive. 

compounds of. 

detection of element. 

Physical examination of solids.. 

Platinic acid test for ammonia. 

potassium. 

Platinum, compounds of. 

detection and properties of... 

metal group.. 

separation from H 2 S group. 

table of reactions with. 

Potassium chloride test for platinum. 

chromate reactions with Ag, Hg, Pb. 

.. 

Bi, Cd, Cu, Hg. 

See HC1 and H 2 S group laboratory exercises. 

compounds of. 

cyanide reactions with Bi, Cd, Cu, Hg^ . 

detection and properties. 

. dichromate test for iodide.. 

ferricyanide test for ferrous iron. 

tests for Cr, Fe. 

Co, Ni, Mn, Zn. 

See also exercises under metals. 

test for copper.. 

ferric iron. 

zinc. 

tests for Ag, Hg + , Pb. 

Bi, Cd, Cu, Hg+ +. 

Al, Fe. 

Co, Ni, Mn, Zn. 

See also exercises on metals mentioned. 

iodide test for nitrite. 

platinum. 

nitrite test for cobalt. 

permanganate test for nitrite. 

reactions with reagents. 

sulphocyanate test for cobalt. 

table of reactions. 

Potential series. 

Precipitation, definition of. 

laws governing. 

test for fluoride. 

Pressure, effect on solubilities. 

Prussian blue, test for cyanide. 

Pseudo solution, definition of. 

Pyroantimonate test for sodium. 

Pyrophosphorio acid, property and detection. 

table of reactions with. 


PAGE 

. 189 

. 283 

...189,196 

. 211 

. 147 

. 147 

. 283 

. 295 

.298 

. 75 

.245 

. 297 

. 240 

. 250 

. 242 

. 283 

. 242 

. 144 

. 178 

.87,89 

. 246 

. 249 

. 48 

87, 89, 100 

. 91 

. 241 

. 242 

. 247 

. 249 

. 16* 

. 297 

.85, 102 

. 159 

. 147 

. 81 

. 25S 

. U 

. : 

. 13 

. 19. 

. 

. 17! 

. i 

....145,14: 

. 19' 

. 25 

















































INDEX 


345 


PAGE 

Qualitative analysis, definition of. 1 

Quantitative analysis, definition of........ l 

Questions, reviews of sections. See at close of each group. 

Rare earths, cerium and. 310 

detection of... 313 

properties of. 310 

separations of. 312 

Rarer elements of the alkali group. 322-324 

ammonium sulphide group.310-322 

hydrogen sulphide group.293- 309 

Reaction, definition of. 2 

law for complete. 10 

limits, studies in. *... 210 

Reactions—acid groups. 

barium chloride group.192-179 

organic acid group.209, 210 

silver nitrate group. 176-180 

soluble acid group. 203-206 

tables of. 254-261 

volatile acid group.164-168 

metal groups. 

ammonium carbonate group.129-133 

sulphide group.92-108 

hydrogen chloride group. 37-39 

sulphide group.56-59, 68-73 

soluble metal group.146-148 

rarer elements.293-323 

tables of.240-253 

Reagents, care of. 32 

definition of. 1 

list of—acid solutions. 326 

compounds. 327 

solids. 32 

quantity to be used.. 32 

special, preparation of. 329 

Recording results, suggestion regarding. 23 

Reducing agents, action on chlorate. 203 

test for bismuth. 46 

chromium.97, 194 

molybdenum. 304 

vanadium. 319 

flame. 16 

Reduction, definition of. 3 

of ferric salts. 101 

test for chromate. 97 

sulphate.*. 197 

tin. 55 

zinc. 90 

See also reducing agents. 




















































346 


INDEX 


✓ 

PAGE 

Reduction, test for without the blowpipe.. 1? 

Reinsch’s test for arsenic. 5*. 

Residue, definition of...... i 

Reversible reaction. f 

Rhodium, compounds of... 28 1 

detection of... 301 

solution of alloys of.•. . . 301 

Rubidium, detection of. 32,' 

Ruthinium, compounds.,. 28; 

detection and properties. 30( 

solution of alloys of. 301 

Salicylic acid, salicylate, detection of. 20! 

properties of. 20! 

tabulated tests of. 26 

test for iron.8’ 

Scott’s hydrogen sulphide generator. 6' 

Selenium, compounds of. 28. 

detection of. 30 

properties of. 30 

solubility of. 30 

Separation of the acids— See group in question of the alkali metals.149-15 

alkaline earth metals.134-13: 

ammonium carbonate group.134-13 

sulphide group.109-12 

hydrogen chloride group.40-4 

sulphide.60-63, 74-7 

soluble group metals.149-15 

metal groups.28-31, 230, 23 

Silicate tests for. 16 

Silicic acid, detection of. 16 

properties of. 16 

tabulated tests. 25 

Silicon, compounds. 28 

See silicic acid. 

Silver chloride, distinction from mercurous chloride. 3 

properties of. 3 

coin test for sulphide. 16 

compounds of. 28 

detection and properties of.35-3 

nitrate group. 15 

descriptive. 17 

reaction of members. 17 

Silver nitrate reactions with acids. 254-26 

As, Sb, Sn.244, 24 

table of analysis. 18 

test for arsenate. 19 

bromide.173, x 7 

chloride. 171, 17 

chromate. 19 



















































INDEX 


347 


Silver nitrate test for cyanide. 

ferricyanide... 

ferrocyanide. 

iodide. 

nitrite. 

phosphate. 

tartrate. 

thiocyanate. 

tin. 

Silver, reactions with.... 

tabulated tests with. 

thiocyanate. 

Sodium bismuthate test for manganese. 

carbonate, reactions with Ag, Hg, Pb. 

Bi, Cd, Cu, Hg+ + 

cobaltic nitrate reagent. 

compounds of. 

hydroxide reactions with Ag, Hg, Pb. 

Bi, Cd, Cu, Hg+ + 

Al, Cr, Fe. 

Co Ni, Mn, Zn. . . , 

Ba, Ca, Sr, Mg.. . . 

NHs. 

test for platinum. 

phosphate reactions with Al, Cr, Fe. 

Co, Ni, Mn, Zn. . . 

Ba, Ca, Sr, Mg.. .. 

Li 

properties and detection. . . 

reactions with reagents. 

tabulated tests of. 

thiosulphate test for molybdenum, 

Solid, preliminary examination of. 

Solubility of elements —See element in question. 

product. 

table. 

Soluble acid group. 

basic group. 

H 2 S group, separation from insoluble H 2 S group. 

H 2 S sub-group B. 

reactions of members. 

metal group. See also alkali group. 

Solution, preparation of. 

of alloys. 

substances for acid analysis. 

metal analysis. 

See solubilities under properties of elements. 

laws governing.. 

theory of. 

Spectrum tests of alkaline earths. 


PAGE 

. 178 

. 180 

. 179 

. 177 

. 166 

. 196 

. 210 

. 180 

. 55 

. 38 

. 240 

. 38 

. 88 

. 241 

. 243 

. 330 

. 287 

. 241 

. 243 

. 247 

. 249 

. 250 

. .,. 252 

. 297 

. 247 

. 248 

. 250 

. 252 

. 145 

. 148 

.. 252 

. 304 

. 211 

. 12 

. 262 

. . . __ 156 

. 140 

. 61 

....49, 74-79 
. 68 

222, 228, 233 

.226-228 

.. 233 

. 222 

. 13 

. . .. 4 

........ 127 





















































348 


INDEX 


Spectrum tests of alkalies. 

Splashing, prevention of. 

Stannic acid.. 

Stannite test for bismuth. 

Stannous chloride, preparation of. 

reactions with Ag, Hg+, Pb. 

Bi, Cd, Cu, Hg+ + .. 

test for platinum. 

Starch paste, preservation of. 

Stoppers, notes regarding. 

Strontium, compounds of. 

detection of. 

properties of. 

reactions with reagents. 

sulphate test for barium. 

Suction, directions for filtration. 

Suggestions for laboratory practice. 

Sulphate method for separating halogens. 

properties and detection. See sulphuric acid. 

separation trom sulphite. 

test for barium. 

test for strontium. 

Sulphide, detection and reactions. 

Sulphite properties and detection. 

Sulphocyanate test for cobalt. 

iron. 

Sulphocyanic acid, properties and detection. 

Sulphur, compounds of. 

dioxide, detection of. 

occurrence and properties. 

solubility in water. 

test for molybdenum. 

Sulphuric acid, detection and properties. 

free, detection of. 

reactions with Ag, Hg, Pb. 

tabulated tests for. 

test for acetate. 

acids, table of. 

chlorate. 

tartrate. 

Sulphurous acid, properties and detection. 

tabulated tests for. 

Systematic analysis of substances. 

Tables of reactions, acids. 

metals. 

separation of metals. 

use of, directions for. 

Tannic acid, tests for. 

Tantalum, compounds of.. 


PAGE 

... 144 
... 32 

... 72 

... 46 

... 330 
... 241 
... 243 
... 297 
... 330 
... 32 

... 287 
... 127 
... 127 
132, 250 
... 126 
... 21 
... 24 

... 182 


... 169 
... 126 
.... 128 
... 167 
163, 168 
... 85 

... 87 

175, 259 
... 289 
163, 168 
161, 162 
... 4 

... 304 




















































INDEX 


349 


Tartario acid, detection of. 

properties of. 

Tellurium, compounds of. 

detection of. 

property, solubility. 

Temperature, effect on solubility. .. 
Terms, definitions of chemical. . . 

Test tube. 

brush. 

rack. 

Thallium, compounds of. 

Theory of solution. 

Thiocyanate test for iron. 

silver. 

Thiocyanio acid, detection of. 

properties of. 

Thiosulphate, detection of. 

properties of.. 

test for aluminum. . . 

Thiosulphuric acid, reactions. 

Thorium, compounds of. 

detection of.. 

properties and solution.. . 

Tin, compounds of. 

detection of. 

group. 

properties of... 

reactions with. 

separation. 

table of reactions with. 

Titanium, compounds of. 

detection and properties 
Traces. See element in question. 

Tungsten, compounds of. 

detection of. 

properties and solution. 
Turmeric test for borate. 


PAGE 

209,261 
... 208 
... 289 
... 306 
... 305 
4 
1 

. . .. 20 
.... 23 

.... 23 

. . . . 289 
. . . . 4 

... . 101 
... 36 

.... 180 
.... 175 
.163,168 
.... 163 
.... 82 
.... 259 
.... 289 
.... 316 
.... 315 
.... 288 
. ... 54 

.... 49 

.... 54 

.... 71 

.... 74 

.... 245 
.... 290 
.... 316 

.... 290 
.... 308 
.... 307 
.... 185 


Uranium, compounds of. 

detection of. 

properties and solution. 


290 

318 

317 


Vanadium, compounds of. 

detection. 

properties and solutson 

Verdigris. See Copper. 

Volatile acid group. 

summary of.,, 


... 291 
... 319 
318, 319 
... 48 

155, 157 
.169 


Wall saltpeter. See nitrio acid. 

















































350 


INDEX 


Wash bottle. 

Washing precipitates, definition. . 
Wet methods for copper tests.. .. 

silver tests. 

Work, preparation for laboratory, 


PAGE 
. 20 
2 

. 48 
. 36 
. 32 


Zinc, compounds of. . 

detection of. 

reactions with. 

separation from group. 

tables of reactions with. 

Zirconium, compounds of. 

detection of... 

properties and solution of. 


... 291 
... 90 
... 107 
109-123 
... 248 
... 291 
... 322 
... 321 






















































































































































































































✓ 



















































































































. 

































































































































































V 






































































» 









♦ • 













































































































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-l'he Airplane.8vo, (In Press.) 

Bedell, F., and Pierce, C. A. Direct and Alternating Current 


Beech, F. 


Begtrup, J. The Slide Valve. 

Bender, C. E. Continuous Bridges.. 

-Proportions of Pins Used in Bridges. 

Bengough, G. D. Brass. 

Bennett, H. G. The Manufacture of Leather- 

-Animal Proteids . 

Bernthsen, A. A Text-book of Organic Chemistry. .. .i2mo, 

Bersch, J. Manufacture of Mineral and Lake Pigments. .8vo, *6 oo 


Birchmore, W. H. Interpretation of Gas Analysis.i2mo, 

Blaine, R. G. The Calculus and Its Applications.i2mo, 


Blasdale, W. C. 
Bloch, L. Science 


Quantitative Chemical Analysis. .i2mo, 


Bockmann, F. 


o 

> 

00 

*2 

00 


*5 

oo 


*3 

50 

.. . (In Press.) 

.8vo, 

*2 

oo 

. i6mo, 

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75 

. i6mo, 

o 

75 

.(In Press.) 


*6 

oo 

» (In Press.) 

i2mo, 

* 3 , 50 

. . 8vo, 

*6 

00 

I 2 E 10 , 

*4 

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. .8VO, 

4 

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*8 

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, i2mo, 

*2 

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. i2mo, 

*1 

25 

. i2mo, 

*1 

75 

Chem- 

.i2mo, 

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i2mo, 


50 


*2 

50 

5 . .8vo, 

8 

50 

. .8vo, 

8 

50 

. i2mo, 

*2 

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. i2mo, 

5 

00 

. . 8vo, 

5 

00 

. i2mo, 

i 

50 

alysis. 

i2mo, 

i 

50 

. .8vo, 

3 

50 

.. 8vo, 

*i 

50 


Bottcher, A. Cranes: Their Construction, Mechanical Equip¬ 
ment and Working.4to, ( Reprinting.) 




























D. VAN NOSTRAND COMPANY'S SHORT-TITLE CATALOG 7 


Bottler, M. Modern Bleaching Agents.i2mo, *2 50 

Bottone, S. R. Magnetos for Automobilists.i2mo, *1 00 

-Electro-Motors, How Made and How Used.i2mo, 1 00 

Boulton, S. B. Preservation of Timber.i6mo, o 75 

Bourcart, E. Insecticides, Fungicides and Weedkillers. .8vo, *6 00 

Bourgougnon, A. Physical Problems.i6mo, o 75 

Bourry, E. Treatise on Ceramic Industries.8vo, 6 00 

Bowie, A. J., Jr. A Practical Treatise on Hydraulic Mining.8vo, 5 00 
Bowles, 0 . Tables of Common Rocks.i6mo, o 75 


Bowser, E. A. Elementary Treatise on Analytic Geometry.i2mo, 1 75 
-Elementary Treatise on the Differential and Integral 


Calculus .i2mo, 2 25 

Bowser, E. A. Elementary Treatise on Analytic Mechanics, 

I2H10, 3 00 

-Elementary Treatise on Hydro-mechanics.i2mo, 2 50 

-A Treatise on Roofs and Bridges.i2mo, *2 25 

Boycott, G. W. M. Compressed Air Work and Diving... . 8 vo, *4 25 

Bradford, G. Whys and Wherefores of Navigation. .i2mo, 200 

_Sea Terms and Phrases.nmo, fabrikoid ( In Press.) 

Bragg, E. M. Design of Marine Engines andi Auxiliaries... 4 00 

Brainard, F. R. The Sextant. .i6mo, 

Brassey’s Naval Annual for 1919.8vo, 10 00 

Briggs, R., and Wolff, A. R. Steam-Heating.i6mo, o 75 

Bright, C. The Life Story of Sir Charles Tilson Bright. .8vo, *4 50 

-Telegraphy, Aeronautics and War.8vo, 6 00 

Brislee, T. J. Introduction to the Study of Fuel.8vo, 3 50 

Broadfoot, S. K. Motors Secondary Batteries.i2mo, *0 75 

Broughton, H. H. Electric Cranes and Hoists. 

Brown, G. Healthy Foundations. l6m0 > o 75 

Brown, H. Irrigation.8vo, 6 00 

Brown, H. Rubber. 8v0 > 2 5 ° 

Brown, W. A. Portland Cement Industry. 8 vo, 3 00 

Brown, Wm. N. The Art of Enamelling on Metal. ...i2mo, 2 00 

-Handbook on Japanning......i2mo, *2 00 

-—House Decorating and Painting.i2mo, 2 00 

-History of Decorative Art.i2mo, o 50 

--Dipping, Burnishing, Lacquering and Bronzing Brass 

Ware . I2m0 * ** 5 ® 

,_Workshop Wrinkles . 8v0 > 1 00 




































8 D. VAN NOSTRAND COMPANY'S SHORT-TITLE CATALOG 


Browne, C. L. Fitting and Erecting of Engines.8vo, 

Browne, R. E. Water Meters.i6mo, 

Bruce, E. M. Detection of the Common Food Adulterants, 


*1 50 
o 75 


i2mo, 


1 40 

3 50 
o 75 

1 00 

2 00 
2 00 
2 00 
2 00 

50 
00 


2 50 
*1 25 
*3 00 


Brunner, R. Manufacture of Lubricants, Shoe Polishes and 

Leather Dressings .. • *8vo, * 

Buel, R. H. Safety Valves.i6mo, 

Bunkley, J. W. Military and Naval Recognition Book. .i2mo, 

Burley, G. W. Lathes, Their Construction and Operation, 

i2mo, 

-Machine and Fitting Shop Practice 2 vols..i2mo, each, 

-Testing of Machine Tools.i2mo, 

Burnside, W. Bridge Foundations.i2mo, * 

Burstall, F. W. Energy Diagram for Gas. With text. ..8vo, 

-Diagram sold separately. 

Burt, W. A. Key to the Solar Compass.i6mo, leather, 

Buskett, E. W. Fire Assaying.i2mo, 

Butler, H. J. Motor Bodies and Chasis.8vo, 

Byers, H. G., and Knight, H. G. Notes on Qualitative 

Analysis.( New Edition in Preparation.) 

Cain, W. Brief Course in the Calculus.i2mo, 

--Elastic Arches .i6mo, 

-Maximum Stresses .i6mo, 

-Practical Designing Retaining of Walls.i6mo, 

-Theory of Steel-concrete Arches and of Vaulted Struc¬ 
tures .i6mo, 

-Theory of Voussoir Arches.i6mo, 

-Symbolic Algebra .i6mO; 

Calvert, G. T. The Manufacture of Sulphate of Ammonia 

and Crude Ammonia.i2mo, 

Carey, A. E., and Oliver, F. W. Tidal Lands.8vo, 

Carhart, H. S. Thermo-Electromotive Force in Electric 

Cells .i2mo (In Press.) 

Carpenter, F. D. Geographical Surveying.i6mo, 

Carpenter, R. C., and Diederichs, H. Internal-Combustion 

Engines .8vo, 5 50 

Carpmael, H. Electric Welding and Welding Appliances.4to, 5 00 
Carter, H. A. Ramie (Rhea), China Grass.i2mo, *3 00 


. i2mo, 

*1 

75 

. i6mo, 

0 

75 

. i6mo, 

0 

75 

. i6mo, 

0 

75 

Struc- 

. i6mo, 

0 

75 

. i6mo, 

0 

75 

. i6mo, 

0 

75 

imonia 

. i2mo, 

4 

00 


5 

00 




























D. VAN NOSTRAND COMPANY^ SHORT-TITLE CATALOG 9 

Carter, H. R. Modern Flax, Hemp, and Jute Spinning. .8vo, *3 50 

-Bleaching, Dyeing and Finishing of Fabrics.8vo, *1 25 

Cary, E. R. Solution of Railroad Problems With the Use of 

the Slide Rule.i6mo, 1 25 

Casler, M. D. Simplified Reinforced Concrete Mathematics, 

i2mo, 1 25 

Cathcart, W. L. Machine Design. Part I. Fastenings. .. 8vo, *3 00 
Cathcart, W. L., and Chaffee, J. I. Elements of Graphic 


Statics . 8vo, *3 00 

-Short Course in Graphics.i2mo, 1 50 

Caven, R. M., and Lander, G. D. Systematic Inorganic Chem¬ 
istry .i2mo, 2 23 

Chalkley, A. P. Diesel Engines.8vo, 5 oq 

Chalmers, T. W. The Production and Treatment of Veg¬ 
etable Oils.4-to, 7 50 

--Paper Making and Its Machinery.4to, 8 00 

-The Gyroscopic Compass.8vo, 5 00 

Chamber’s Mathematical Tables.8vo, 2 50 

Chambers, G. F. Astronomy.i6mo, *1 jjo 

Chappel, E. Five Figure Mathematical Tables.8vo, 2 50 

Charnock. Mechanical Technology.8vo, *3 50 

Charpentier, P. Timber.8vo, *6 00 

Chatley, H. Principles and Designs of Aeroplanes.i6mo, o 75 

-How to Use Water Power.. i2mo, *1 50 

—*—Gyrostatic Balancing .8vo, *1 25 

Child, C. D. Electric Arc.8vo, *2 00 

Christian, M. Disinfection and Disinfectants.i2mo, 2 50 

Christie, W. W. Boiler-waters, Scale, Corrosion, Foaming, 

8vo, *3 00 

-Chimney Design and Theory.8vo, *3 00 

-Furnace Draft .i6mo, o 75 

-Water, Its Purification and Use in Industries.8vo, 3 00 

Cisin, H. J. Modern Marine Engineering. i2mo, fabrikoid (In Press ) 

Church’s Laboratory Guide.8vo, 2 50 

Clapham, J. H. Woolen and Worsted Industries.8vo, 2 oc 


Clark, A. G. Motor Car Engineering. 

Vol. I. Construction. *4 00 

Vol. II. Design. 3 5 ° 

Clark, C. H. Marine Gas Engines. New Edition. 2 00 




































10 D. VAN NOSTRAND COMPANY^ SHORT-TITLE CATALOG 


Clark, J. W., and Scott, W. Plumbing Practice. 

Vol. I. Lead Working and Plumbers’ Materials. .8vo, *4 oo 

Vol. II. Sanitary Plumbing and Fittings. (In Press.) 

Vol. III. Practical Lead Working on Roofs. (In Press.) 

Clarkson, R. P. Elementary Electrical Engineering. (In Press.) 

Clerk. D., and Idell, F. E. Theory of the Gas Engine. 

* i6mo, 

Clevenger, S. R. Treatise on the Method of Government 

Surveying . .i6mo, mor., 

Clouth, F. Rubber, Gutta-Percha, and Balata.8vo, 

Cochran, J. Treatise on Cement Specifications.8vo, 

_Concrete and Reinforced Concrete Specifications-8vo, *2 50 


o 75 

2 50 
*6 00 
*1 00 


Cocking, W.C. Calculations of Steel-Frame Structures.nmo, 2 50 
Coffin, J. H. C. Navigation and Nautical Astronomy. .i2mo, *3 00 


Colburn, Z., and Thurston, R. H. Steam Boiler Explosions. 

i6mo, o 75 

Cole, R. S. Treatise on Photographic Optics.i2mo, 2 00 

Coles-Finch, W. Water, Its Origin and Use. 8 vo, 3 5 ° 

Collins, C. D. Drafting Room Methods, Standards and 

Forms.8vo, 2 00 

Collins, J. E. Useful Alloys and Memoranda for Goldsmiths, 

Jewelers.i6mo, o 50 

Collins, S. Hoare. Plant Products and Chemical Fertilizers, 

8vo, 3 00 

-Chemical Fertilizers and Parasiticides. 3 5 ° 

Collis, A. G. High and Low Tension Switch-Gear Design.8vo, *3 50 

-.Switchgear .i2mo, o 50 

Colver, E. D. S. High Explosives.8vo, 12 50 

Comstock, D. F., and Troland, L. T. The Nature of Matter 

and Electricity.i2mo, 2 50 

Coombs, H. A. Gear Teeth. o 75 

Cooper, W. R. Primary Batteries. 8 vo, *6 00 

Copperthwaite, W. C. Tunnel Shields.4to, *9 00 

Corfield, W. H. Dwelling Houses.i6mo, o 75 

--Water and Water-Supply. ....i 6 mo, o 75 

Cornwall, H. B. Manual of Blow-pipe Analysis.... 8 vo, *2 50 

Couch, J. F. Dictionary of Chemical Terms..... .i2mo, 3 00 


Cowee, G. A. Practical Safety Methods and Devices-8vo, 4 00 






















D. VAN NOSTRAND COMPANY^ SHORT-TITLE CATALOG II 


Cowell, W. B. Pure Air, Ozone, and Water.i2mo, *2 50 

Craig, J. W., and Woodward, W. P. Questions and Answers 

About Electrical Apparatus.i2mo, leather, 1 50 

Craig, T. Motion of a Solid in a Fuel.i6mo, o 75 

-Wave and Vortex Motion.i6mo, o 75 

Crehore, A. C. Mystery of Matter and Energy.12010, 1 00 

-The Atom..•.12010, 2 00 

Crocker, F. B., and Arendt, M. Electric Motors.8vo, *2 50 

-and Wheeler, S. S. The Management of Electrical 

Machinery .i2mo, *1 00 

Crosby, E. U., Fiske, H. A., and Forster, H. W. Handbook 

of Fire Protection.i2mo, 4 00 

Cross, C. F., Bevan, E. J., and Sindall, R. W. Wood Pulp 

and Its Uses.8vo, 3 50 

Crosskey, L. R. Elementary Perspective.8vo, 1 3 o 

Crosskey, L. R., and Thaw, J. Advanced Perspective.... 8vo, 2 00 

Culley, J. L. Theory of Arches.i6mo, o 75 

Cushing, H. C., Jr., and Harrison, N. Central Station Man¬ 
agement . 00 


Dadourian, H. M. Analytical Mechanics.8vo, 

-Graphic Statics.8vo, 

Danby, A. Natural Rock Asphalts and Bitumens.8vo, 

Darling, E. R. Inorganic Chemical Synonyms.i2mo, 

Davenport, C. The Book.8vo, 

Davey, N. The Gas Turbine.8vo, 

Davies, F. H. Electric Power and Traction.8vo, 

-Foundations and Machinery Fixing.i6mo 


Deerr, N. Sugar Cane.8vo, 

Deite, C. Manual of Toilet Soap-Making.8vo, 

De la Coux, H. The Industrial Uses of Water.8vo, 

Del Mar, W. A. Electric Power Conductors.8vo, 

Denny, G. A. Deep-Level Mines of the Rand.4to, 

De Roos, J. D. C. Linkages.i6mo, 

Derr, W. L. Block Signal Operations. Oblong i2mo, 

Desaint, A. Three Hundred Shades and How to Mix Them. 

8vo, 


De Varona, A. Sewer Gases.i6mo, 

Devey, R. G. Mill and Factory Wiring.i2mo, 


3 75 
o 75 
*2 50 

1 00 

2 50 
*4 00 
*2 00 
*1 00 
10 00 

7 00 
*5 00 
*2 00 
*10 00 
o 75 
*1 50 

9 00 
o 75 
*r 00 


































12 D, VAN NOSTRAND COMPANY^ SHORT-TITLE CATALOG 


Dichnian, C. Basic Open-Hearth Steel Process. 8 vo, 4 °° 

Dieterich. K. Analysis of Resins, Balsams, and Gum Resins. 

8 vo, *3 5 ° 

Dilworth, E. C. Steel Railway Bridges. qto, 6 00 

Dinger, Lieut. H. C. Care and Operation of Naval Ma¬ 
chinery .12010, 3 00 

Dixon, D. B. Machinist’s and Steam Engineer’s Practical 

Calculator .i6mo, mor., 1 25 

Dommett, W. E. Motor Car Mechanism.12010, *2 00 


Dorr, B. F. The Surveyor’s Guide and Pocket Table-book. 

i6mo., mor., 2 00 

Draper, C. H. Heat and the Principles of Thermo-dynamics, 

12010, 2 25 

Draper, E. G. Navigating the Ship. i2mo, 2 00 

Dubbel, H. High Power Gas Engines.8vo, *5 00 

Dumesny, P., and Noyer, J. Wood Products, Distillates, and 

Extracts .8vo, *5 00 

Duncan, W. G., and Penman, D. The Electrical Equipment of 

Collieries . 8vo, *5 00 


Dunkley, W. G. Design of Machine Elements. 2 vols. 

i2mo, each, *2 od 

Dunstan, A. E., and Thole, F. B. T. Textbook of Practical 


Chemistry . 12010, 3 00 

Durham, H. W. Saws.8vo, 2 50 

Duthie, A. L. Decorative Glass Processes.8vo, 2 50 

Dwight, H. B. Transmission Line Formulas.8vo, 2 00 

Dyke, A. L. Dyke’s Automobile and Gasoline Engine 

Encyclopedia .8vo, 6 00 

Dyson, S. S. and Clarkson, S. S. Chemical Works.8vo, 9 00 

-A Manual of Chemical Plant. 12 parts...,4to, paper, 7 50 

Eccles, W. H. Wireless Telegraphy and Telephony. . i2mo, 7 00 

Eck, J. Light, Radiation and Illumination.8vo, *2 50 

Eddy, H. T. Maximum Stresses Under Concentrated Loads, 

8vo, 1 50 

Edelman, P. Inventions and Patents.12010, *1 50 

Edgecumbe, K. Industrial Electrical Measuring Instruments,. 

8 vo, 5 00 

Edler, R. Switches and Switchgear.8vo, *4 00 





















D. VAN NOSTRAND COMPANY'S SHORT-TITLE CATALOG 13 


Eissler, M. The Metallurgy of Gold.8vo, 9 00 

-The Metallurgy of Silver.8vo, 4. 00 

-The Metallurgy of Argentiferous Lead.8vo, 6 25 

-A Handbook of Modern Explosives.8vo, 5 00 

Ekin, T. C. Water Pipe and Sewage Discharge Diagrams, 

folio, *3 00 

Electric Light Carbons, Manufacture of.8vo, 1 00 

Eliot, C. W., and Storer, F. H. Compendious Manual of Qualita¬ 
tive Chemical Analysis.i2mo, 1 50 

Eliott, A. W. M. Rectangular Areas.12010, 3 00 

Ellis, C. Hydrogenation of Oils. 8 vo, 7 5 ° 


-Ultraviolet Light, its Application in Chemical Arts, 

i2mo (In Press.) 

-and Meigs, J. V. Gasolene and Other Motor Fuels. 

(In Preparation.) 


Ellis, G. Modern Technical Drawing. 8 vo, *2 00 

Ennis, Wm D. Linseed Oil and Other Seed Oils. 8 vo, 5 00 

-Applied Thermodynamics. 8vo, 500 

-Flying Machines To-day.i2mo, *1 50 

-Vapors for Heat Engines.i2mo, *1 00 

Ermen, W. F. A. Materials Used in Sizing.8vo, *2 00 

Erwin, M. The Universe and the Atom.1200 ( Reprinting) 

Ewing, A. J. Magnetic Induction in Iron. 8 vo, *5 00 

Fage, A. Airscrews in Theory and Practice. *4to, 10 00 

Fairchild, J. F. Graphical Compass Conversion Chart and 

Tables . 0 5© 

Fairie J. Notes on Lead Ores....i2mo, o 50 

_Notes on Pottery Clays.....lamo, *200 

Fairley, W., and Andre, Geo. J. Vertilation of Coal Mines. 

i6mo, o 75 

Fairweather, W C. Foreign and Colonial Patent Laws .. .8vo, *3 00 

Falk K. G. Chemical Reactions: Their Theory and Mechanism, 

i2mo, 2 50 

Fanning, J. T. Hydraulic and Water-supply Engineering.8vo, *5 00 

Farnsworth, P. V. Shop Mathematics.lamo (In Press.) 

Fay, I. W.’ The Coal-tar Dyes..8vo, 5 00 

Fernbach, R. L. Glue and Gelatine..8vo, *3 00 

Findlay, A. The Treasures of Coal Tar.i2mo, 2 00 

Firth, J. B. Practical Physical Chemistry.izmo, *1 25 
































14 D. VAN NOSTRAND COMPANY'S SHORT-TITLE CATALOG 


Fischer, E. The Preparation of Organic Compounds. .i2mo, 2 00 
Fisher, H. K. C., and Darby, W. C. Submarine Cable Testing. 


8vo, *4 00 

Fleischmann, W. The Book of the Dairy.8vo, 4 50 

Fleming, J. A. The Alternate-current Transformer. Two 

Volumes.8vo, 

Vol. I. The Induction of Electric Currents. *6 50 

Vol. II. The Utilization of Induced Currents. *6 50 

Fleming, J. A. Propagation of Electric Currents.8vo, 5 00 


-A Handbook for the Electrical Laboratory and Testing 

Room. Two Volumes.8vo, each, *6 50 

Fleury, P. Preparation and Uses of White Zinc Paints..8vo, 3 00 

Flynn, P. J. Flow of Water.i2ino, o 75 

——Hydraulic Tables .i6mo, 075 

Foster, U. A. Electrical Engineers’ Pocket-book. (Seventh 

Q2 y Edition.). .i2mo, leather, 5 00. 

-^—Engineering Valuation of Public Utilities and Factories, 


.»£ (* ./ 8vo, *3 00 

Fowle, F. F. Overhead Transmission Line Crossings ... .i2mo, *1 50 

The Solution of Alternating Current Problems.8vo (In Press.) 

Fox, W. G. Transition Curves. o 75 

Fox, W., and Thomas, C. W. Practical Course in Mechanical 

Drawing.nmo, 1 25 

Foye, J. C. Chemical Problems.i6mo, o 75 

-Handbook of Mineralogy.i6mo, o 75 

Francis, J. B. Lowell Hydraulic Experiments.4to, 15 00 

Franzen, H. Exercises in Gas Analysis.i2mo J *1 00 

Fraser, E. S., and Jones, R. B. Motor Vehicles and Their 

Engines .8vo, fabrikoid, 2 00 

Freudemacher, P. W. Electrical Mining Installations.. i2mo, *1 00 

Friend, J. N. The Chemistry of Linseed Oil.i2mo, 1 00 

Fritsch, J. Manufacture of Chemical Manures.8vo, *5 00 

Frye, A. I. Civil Engineers’ Pocket-book.i2mo, leather, *5 00 

Fuller, G. W. Investigations into the Purification of the Ohio 

River.4to, *10 00 

Furnell, J. Paints, Colors, Oils, and Varnishes.8vo, 



























D. VAN NOSTRAND COMPANY^ SHORT-TITLE CATALOG 15 


*2 50 
3 00 

*5 00 

I 50 
*6 00 
o 75 

3 50 
*6 00 
00 

5° 
50 
00 
50 


Gant, L. W. Elements of Electric Traction.8vo, 

Garcia, A. J. R. V. Spanish-English Railway Terms. .8vo, 
Gardner, H. A. Paint Researches and Their Practical 
Application .8vo, 

Garforth, W. E. Rules for Recovering Coal Mines after Explo¬ 
sions and Fires.i2mo, leather, 

Garrard, C. C. Electric Switch and Controlling Gear....8vo, 

Gaudard, J. Foundations.i6mo, 

Gear, H. B., and Williams, P. F. Electric Central Station Dis¬ 
tributing Systems .8vo, 

Geerligs, H. C. P. Cane Sugar and Its Manufacture.8vo’ 

-Chemical Control in Cane Sugar Factories. 4 to, 

Geikie, J. Structural and Field Geology.8vo, 

-Mountains, Their Origin, Growth and Decay.svo* 

- The Antiquity of Man in Europe.8vo, 

Georgi, F., nd Schubert, A. Sheet Metal Working... .8vo, 
Gerhard, W. P. Sanitation, Water-supply and Sewage Dis¬ 
posal of Country Houses.i2mo, 

-Gas Lighting .i6mo, 

-House Drainage . i6mo, 

-Household Wastes ..i6mo, 

--Sanitary Drainage of Buildings.i6mo, 

Gerhardi, C. W. H. Electricity Meters.8vo, 

Geschwind, L. Manufacture of Alum and Sulphates. .. .8vo, 
Gibbings, A. H. Oil Fuel Equipment for Locomotives. .8vo, 

( Reprinting) 

Gibbs, W. E. Lighting by Acetylene.i2mo, *1 50 

Gibson, A. H. Hydraulics and Its Application.8vo, 

-Water Hammer in Hydraulic Pipe Lines.i2mo, 

Gibson, A. H., and Ritchie, E. G. Circular Arc Bow Girder. 4 to, 

Gilbreth, F. B. Motion Study.i2mo, 

-Primer of Scientific Management.i2mo, 

Gillmore, Gen. Q. A. Roads, Streets, and Pavements.. .i2mo, 
Godfrey, E. Tables for Structural Engineers. .i6mo, leather, 

Golding, H. A. The Theta-Phi Diagram...i2mo, 

Goldschmidt, R. Alternating Current Commutator Motor. 8vo, 
Goodchild, W. Precious Stones.8vo, 


50 

75 
75 
75 
75 
*7 20 

*5 00 


*6 00 
2 50 
*3 50 
*2 00 
00 

25 

50 
00 
00 
50 

























1 6 D. VAN NOSTRAND COMPANY^ SHORT-TITLE CATALOG 


Goodell, J. M. The Location, Construction and Maintenance 


of Roads . 8vo, 2 00 

Goodeve, T. M. Textbook on the Steam-engine.i2mo, 2 50 

Gore, G. Electrolytic Separation of Metals.Svo, 4 5 ° 

Gould, E. S. Arithmetic of the Steam-engine.i2mo, 1 00 

-Calculus .; .i6mo, 075 

-High Masonry Dams.i6mo, o 75 

-Practical Hydrostatics and Hydrostatic Formulas. .i6mo, o 75 

Goulding, E. Cotton and Other Vegetable Fibres.8vo, 3 00 

Gratacap, L. P. A Popular Guide to Minerals.8vo, *2 00 

Gray, H. H. Gas-Works Products. . ...8vo {In Press.) 

Gray, J. Electrical Influence Machines.i2mo, 200 

Gray, J. Marine Boiler Design.i2mo, ( Reprinting.) 

Greenhill, G. Dynamics of Mechanical Flight.8vo. *2 50 

Greenwood, H. C. The Industrial Gases.8vo, 5 00 

Gregorious, R. Mineral Waxes. izmo, *3 00 

Grierson, R. Modern Methods of Ventilation.8vo, 3 00 

Griffiths, A. B. A Treatise on Manures.i2mo, {Reprinting.) 

Gross, E. Hops.8vo, *5 00 

Grossman, J. Ammonia and its Compounds.nmo, 1 50 

Groth, L. A. Welding and Cutting Metals by Gases or Electric¬ 
ity . 8vo, 3 00 

Grover, F. Modern Gas and Oil Engines.8vo, *3 00 

Gruner, A. Power-loom Weaving.8vo, *3 50 

Grunsky, C. E. Topographic Stadia Surveying.i2mo, 2 00 

Gunther, C. 0 . Integration.8vo, 1 50 

Gurden, R. L. Traverse Tables.folio, half mor., *7 50 

Guy, A. E. Experiments on the Flexure of Beams.8vo, *1 25 


Haenig, A. Emery and the Emery Industry.8vo, *2 50 

Hainbach, R. Pottery Decoration.:.i2mo, *3 50 

Hale, A. J. The Manufacture of Chemicals by Electrolysis, 

8vo, 2 00 

Hale, Harrison. American Chemistry.i2mo, {In Press) 

Hale, W. J. Calculations of General Chemistry.nmo, 1 50 

Hall, C. H. Chemistry of Paints and Paint Vehicles.nmo, *2 00 

Hall, R. H. Governors and Governing Mechanism.i2mo, *2 50 

































D. VAN NOSTRAND COMPANY’S SHORT-TITLE CATALOG 17 


Hall, W. S. Elements of the Differential and Integral Calculus 


8vo, 


2 75 
4 oo 

*1 25 
1 50 
o 75 
o 75 


Descriptive Geometry.8vo volume and 4to atlas) 

Haller, G. F., and Cunningham, E. T. The Tesla Coil.1 2 mo, 

Halsey, F. A Slide Valve Gears. I2mo ' 

-The Use of the Slide Rule. l6mo ’ 

-Worm and Spiral Gearing. l6mo ) 

Hamlin, M. L. Action of Chemicals on Industrial Materials) 

i2mo, (In Press.) 

Hancock, H. Textbook of Mechanics and Hydrostatics..... 8vo, i 50 

Hardy, E. Elementary Principles of Graphic Statics.i2mo, *1 qo 

Haring, H. Engineering Law 

Vol. I. Law of Contract. 8 v 0 , * 4 oo 

Harper, J H. Hydraulic Tables on the Flow of Water. i6mo, *2 00 

Harris, S. M. Practical Topographical Surveying. U n Press ) 

Harrow, B. Eminent Chemists of Our Times: Their Lives 

and Work . . p 

-From Newton to Einstein. i2mo i oo 

Harvey, A. Practical Leather Chemistry.. . . . . . ..8vo) 600 

Haskins, C. H. The Galvanometer and Its Uses.i6mo, 


1 50 

.square i2mo, *1 50 


Hatt, J. A. H. The Colorist. 

Hausbrand, E. Drying by Means of Air and Steam.. i 2 mo *2 50 

-Evaporating, Condensing and Cooling Apparatus. .8vo* *600 

Hausmann, E. Telegraph Engineering.8vo, *3 00 

Hausner, A. Manufacture of Preserved Foods and Sweetmeats. 


Hawkesworth, J. Graphical Handbook for Reinforced Concrete 

Design . . 

Hay, A. Continuous Current Engineering.Svo* 

Hayes, H. V. Public Utilities, Their Cost New and Deprecia- 


8vo, *3 50 


k 2 OO 

3 75 


tion. 


8vo, 


-Public Utilities, Their Fair Present Value and Return, 

Heath, F. H. Chemistry of Photography.8vo (In*Press') 

Heather, H. J. S. Electrical Engineering. 8vo *4 r 0 

Heaviside, 0 . Electromagnetic Theory. ' * D 

v°! S ',fr and 11 . 8v °. each, ( Reprinting .) 

T#L 111 .8vo, ( Reprinting .) 






















1 8 D. VAN NOSTRAND COMPANY^ SHORT-TITLE CATALOG 

Heck, R. C. H. Steam Engine and Turbine.8vo, 4 50 

-Steam-Engine and Other Steam Motors. Two Volumes. 

Vol. I. Thermodynamics and Mechanics.8vo, 4 5 ° 

Vol. II. Form Construction and Working.i8vo, 5 50 

-Notes on Elementary Kinematics.. . 8vo, boards, *1 00 

-Graphics of Machine Forces..8vo, boards, *1 00 

Heermann, P. Dyers’ Materials.i2mo, *3 00 

H e llot, Macquer and D’Apligny. Art of Dyeing Wool, Silk and 

Cotton.8vo, *2 00 

Hering, C., and Getmann, F. H. Standard Tables of Electro¬ 
chemical Equivalents.. *2 00 

Hering, D. W. -Essentials of Physics for College Students. 


8vo, *2 25 

Herington, C. F. Powdered Coal as a Fuel.8vo, 3 00 

Hermann, G. The Graphical Statics of Mechanism. . i2mo, 200 
Herzfeld, J. Testing of Yarns and Textile Fabrics.8vo, 

{New Edition in Preparation.) 

Hildenbrand, B. W. Cable-Making.i6mo, o 75 

Hilditch, T. P. Concise History of Chemistry.i2mo, *1 50 

Hill, C. W. Laboratory Manual and Notes in Beginning 

Chemistry . {In Press.) 

Hill, M. J. M. The Theory of Proportion.8vo, *2 50 

Hillhouse, P. A. Ship Stability and Trim.8vo, 5 00 

Hiroi, I. Plate Girder Construction.i6mo, o 75 

-Statically-Indeterminate Stresses.i2mo, 2 50 

Hirshfeld, C. F. Engineering Thermodynamics.i6mo, o 75 

Hoar, A. The Submarine Torpedo Boat.12010, *2 00 

Hobart, H. M. Heavy Electrical Engineering.8vo, *4 50 

-Design of Static Transformers.i2mo, *2 50 

-Electricity.8vo, *2 00 

t -Electric Trains.8vo, {Reprinting.) 

-Electric Propulsion of Ships.8vo, *2 50 


Hobart, J. F. Hard Soldering, Soft Soldering, and Brazing. 

i2mo, 1 25 

Hobbs, W. R. P. The Arithmetic of Electrical Measurements 

12010, o 75 































D. VAN NOSTRAND COMPANY^ SHORT-TITLE CATALOG 19 


Hoff, J. N. Paint and Varnish Facts and Formulas. .. .i2mo, 2 00 

Hole, W. The Distribution of Gas.8vo, *8 50 

Hopkins, N. M. Model Engines and Small Boats.i2mo, 1 25 

-The Outlook for Research and Invention. ..i2mo, 2 00 

Hopkinson, J., Shoolbred, J. N., and Day, R. E. Dynamic 

Electricity . l6m0 > 0 75 

Horner, J. Practical Ironfounding.8vo, *2 00 

_Gear Cutting, in Theory and Practice..8vo, ( Reprinting .) 

Houghton, C. E. The Elements of Mechanics of Materials, 

: i2mo, 2 50 

Houstoun, R. A. Studies in Light Production.i2mo, 2 00 

Hovenden, F. Practical Mathematics for Young Engineers, 

i2mo, *1 50 

Howe, G. Mathematics for the Practical Man.i2mo, 1 50 

Howorth, J. Repairing and Riveting Glass, China and Earthen¬ 
ware ...8vo, paper, *0 50 

Hoyt, W. F. Chemistry by Experimentation..i2tno, *0 70 

Hubbard, .E. The Utilization of Wood-waste.8vo, *2 50 

Hubner, J. Bleaching and Dyeing of Vegetable and Fibrous 

Materials . 8v0 » 7 5 °. 

Hudson, 0 . F. Iron and Steel.8vo, *2 50 

Humphreys, A. C. The Business Features of Engineering 

Practice . 8v0 * 2 5 ° 


Hunter, A. Bridge Work. 7 .• • 8v0 In 

Hurst, G. H. Handbook of the Theory of Color....8vo, 

_Dictionary of Chemicals and Raw Products.8vo, 

_ Lubricating Oils, Fats and Greases..8vo, 

•-Soaps . 8v0 ’ 

Hurst, G. H., and Simmons, W. H. Textile Soaps and Oils, 

8vo, 

Hurst, H. E., and Lattey, R. T. Text-book of Physics 8vo, 

-Also published in Three Parts: 

Vol I. Dynamics and Heat. 

Vol. II. Sound and Light.. 

Vol. III. Magnetism and Electricity. 


Press.) 
*3 5o 
*5 00 
*5 00 
*6 00 

3 5o 
*3 00 

2 50 
2 50 
2 50 





























20 D. VAN NOSTRAND COMPANY^ SHORT-TITLE CATALOG 


Hutchinson, R. W., Jr. Long Distance Electric Power Trans¬ 
mission.i2mo, *3 oo 


Hutchinson, R. W., Jr., and Thomas, W. A. Electricity in 


Mining. (In Press.) 

Hyde, E. W. Skew Arches.i6mo, o 75 

Hyde, F. S. Solvents, Oils, Gums and Waxes.8vo, *2 00 

Induction Coils . i6mo, o 75 

Ingham, A. E. Gearing. A practical treatise.8vo, *2 50 

Ingle, H. Manual of Agricultural Chemistry.8vo, 5 00 

Inness, C. H. Problems in Machine Design.i2mo, *3 00 

-Centrifugal Pumps .i2mo, *3 00 

-The Fan .iamo, *4 00 

Jacob, A., and Gould, E. S. On the Designing and Construction 

of Storage Reservoirs.i6mo, o 75 

Jacobs, F. B. Cam Design and Manufacture. (In Press.) 

James, H. D. Controllers for Electric Motors.8vo, 3 00 

Jehl, F. Manufacture of Carbons.8vo, 5 00 

Jennings, A. S. Commercial Paints and Painting. .. .8vo, 250 

Jennison, F. H. The Manufacture of Lake Pigments... .8vo, 600 

Jepson, G. Cams and the Principles of their Construction.. .8vo, *1 50 

-Mechanical Drawing..8vo (In Preparation.) 

Jervis-Smith, F. J. Dynamometers.8vo, *4 00 

Jockin, W. Arithmetic of the Gold and Silversmith... . i2mo, *1 00 
Johnson, C. H., and Earle, R. P. Practical Tests for the 

Electrical Laboratory . (In Press.) 

Johnson, J. H. Arc Lamps and Accessory Apparatus. .i2mo, *0 75 
Johnson, T. M. Ship Wiring and Fitting.i2mo, (Reprinting.) 


Johnston, J. F. W., and Cameron, C. Elements of Agricultural 


Chemistry and Geology..i2mo, 2 60 

Joly, J. Radioactivity and Geology.i2mo, (Reprinting.) 

Jones, H. C. Electrical Nature of Matter and Radioactivity 

i2mo, 2 25 

-Nature of Solution....;.Svo, 375 

-New Era in Chemistry.i2mo, *2 00 

Jones, J. H. Tinplate Industry.8vo, *3 00 

























D. VAN NOSTRAND COMPANY'S SHORT-TITLE CATALOG 21 


>nes, M. W. Testing Raw Materials Used in Paint-iamo. * 

Drdan, L. C. Practical Railway Spiral.i2mo, Leather, * 

iptner, H. F. V. Siderology; The Science of Iron.8vo, * 


Weaving 


Hrkaldy, A. W„ and Evans, A. D. History and Economics 


of Transport. 


app, G. Alternate Current Machinery.i6mo, 

apper, F. Overhead Transmission Lines.4to, 

ieim A. W. Prevention of Dampness lh Buildings. .. .8vo, 
ieller, S. S., and Knox, W. E. Analytical Geometry and 

Calculus ... 

lemble, W. T., and Underhill, C. R. The Periodic Law and the 

Hydrogen Spectrum.8vo, paper, * 

lemp, J. F. Handbook of Rocks.8vo, * 

Kennedy, A. B. W., and Thurston, R. H. Kinematics of 

Machinery .i6mo, 

lennedy, A. B. W., Unwin, W. C., and Idell, F. E. Compressed 

Ai r . l6mo » 

lennedy, R. Flying Machines; Practice and Design..i2mo, 

_Principles of Aeroplane Construction...8vo, 5 

lent, W. Strength of Materials..i6mo, 

Kershaw, J. B. C. Fuel, Water and Gas Analysis ....8vo, 

-^Electrometallurgy .• • ■ • • • • ■ ■ ■ • • • • :? v ®» 

- .Electro-Thermal Methods of Iron and Steel Production, 

__The Use of Low-Grade and Waste Fuels for. Power 

Generation . ••.••• . 

Cingzett. C. T. Popular Chemical Dictionary.8vo, 

Cinzbrunner, C. Continuous Current Armatures .8vo, 

_Testing of Alternating Current Machines.8vo, * 

Cinzer, H. and Walter K. Theory and Practice of Damask 


.8vo, 


8vo, 


Eirkbride, J. Engraving for Illustration.8vo, 

Kirschke, A. Gas and Oil Engines." m0 ’ 

Klein, J. F. Design of a High speed Steam-engine.8vo, 

_Physical Significance of Entropy. 

Klingenberg, G. Large Electric Power Stations.4to, 


2 50 

1 50 
5 oo 

o 75 
4 oo 

2 50 

2 OO 

o 50 

1 50 

o 75 

o 75 

2 50 

K 2 00 
o 75 

3 50 

2 50 

3 00 

4 00 
4 00 
1 50 

! 2 00 

4 OO 

*3 OO 
*1 OO 
1 50 
*5 00 
*1 50 

9 00 





























22 D. VAN NOSTRAND COMPANY'S SHORT-TITLE CATALOG 


Knight, R.-Adm. A. M. Modern Seamanship.. .8vo, *65 

——Pocket Edition.fabrikoid, i2mo, 3 o 

Knott, C. G., and Mackay, J. J. Practical Mathematics. .8vo, 2 51 

Knox, J. Physico-chemical Calculations.i2mo, 1 51 

-Fixation of Atmospheric Nitrogen.i2mo, 1 01 

Koester, F. Steam-Electric Power Plants.4to, *5 o: 

-Hydroelectric Developments, and Engineering.4to, 6 o< 

Roller, T. The Utilization of Waste Products.8vo, *5 01 

-Cosmetics .8vo, 3 51 

Koppe, S. W. Glycerine.i2mo, *3 51 

Kozmin, P. A. Flour Milling.8vo, 8 s< 

Krauch, C. Chemical Reagents.8vo, 7 o< 

Kremann, R. Application of Physico Chemical Theory to 
Technical Processes and Manufacturing Methods. 

8vo, *3 o< 

Kretchmar, K. Yarn and Warp Sizing.8vo, *5 o< 


Laffargue, A. The Attack in Trench Warfare.32010, o 5c 

Lallier, E. V. Elementary Manual of the Steam Engine. 

i2mo, *2 oc 

Lambert, T. Lead and its Compounds.8vo, *3 5c 

-Bone Products and Manures.8vo, *3 5c 

Lamborn, L. L. Cottonseed Products.8vo, 4 oc 

-Modern Soaps, Candles, and Glycerin.8vo, 10 oc 

Lamprecht, R. Recovery Work After Pit Fires.Svo, *5 oc 

Lanchester, F. W. Aerial Flight. Two Volumes. 8vo. 

Vol. I. Aerodynamics .*6 oc 

Vol. II. Aerodonetics. *6 oc 

-The Flying Machine.8vo, *3 oc 

— Industrial Engineering: Present and Post-War Outlook, 

i2mo, 1 00 

Lange, K. R. By-Products of Coal-Gas Manufacture.. i2mo, 2 50 

La Rue, B. F. Swing Bridges.161110, o 75 

Lassar-Cohn, Dr. Modern Scientific Chemistry.i2mo, 2 25 

Latimer, L. H., Field, C. T., and Howell, J. W. Incandescent 

Electric Lighting .i6mo, 0 75 



























D. VAN NOSTRAND COMPANY^ SHORT-TITLE CATALOG 23 


Latta, M. N. Handbook of American Gas-Engineering Practice. 

8vo, *5 oo 

_American Producer Gas Practice . ..• • • 4to, *6 oo 

Laws, B. C. Stability and Equilibrium of Floating Bodies. 8vo, 4 50 
Lawson, W. R. British Railways, a Financial and Commer¬ 
cial Survey .•*;- 8v0 ». 2 °° 

Leask A. R. Refrigerating Machinery.i2mo, ( Reprinting.) 

Lecky S. T. S. “Wrinkles” in Practical Navigation-8vo, *10 00 

-Danger Angle .. 2 50 

—^-Pocket Edition .. 5 00 

Le Doux, M. Ice-Making Machines.i6mo, o 75 

Leeds, C. C. Mechanical Drawing for Trade Schools.oblong 4to, 2 25 

_Mechanical Drawing for High and Vocational Schools, 

4to, *1 50 

_Principles of Engineering Drawing.8vo, 2 00 

Lefevre, L. Architectural Pottery.4to, *7 00 

Lehner, S. Ink Manufacture...?. 8v0 ’ * 2 5 ° 

Lemstrom, S. Electricity in Agriculture and Horticulture.. 8 vo, * 1 50 

Letts, E. A. Fundamental Problems in Chemistry.8vo, *2 00 

Le Van, W. B. Steam-Engine Indicator.i6mo, o 75 

Lewes V. B. Liquid and Gaseous Fuels.8vo, 3 00 

_Carbonization of Coal. 8v0 > 5 00 

Lewis Automatic Machine Rifle ; Operation of.i6mo, *0 60 

Licks, H. E, Recreations in Mathematics.i2mo, 1 50 

Lieber B. F- Lieber’s Five Letter Standard Telegraphic Code, 

_-—English Edition . 8v0 ’ , 15 00 

-Terminal Index . • $ 

-Lieber’s Appendix . follo » * 5 00 

__Handy Tables . ••••••••*• V ' 2 50 

_Bankers and Stockbrokers’ Code and Merchants and 

Shippers’ Blank Tables . 8v0 » J 5 00 

_100,000,000 Combination Code. 8v0 > * IQ 00 

Livermore, V. P., and Williams, J. How to Become a Com¬ 
petent .. I2mo ’ ' 1 00 































24 D. VAN NOSTRAND COMPANY'S SHORT-TITLE CATALOG 


Livingstone, R. Design and Construction of Commutators, 

>v 8vo, 

-Mechanical Design and Construction of Generators. .8vo, 

Lloyd, S. L. Fertilizer Materials .i2mo, 

Lockwood, T. D. Electricity, Magnetism, and Electro-teleg¬ 
raphy.8vo, 

Electrical Measurement and the Galvanometer.... i2mo, 


4 So 
4 50 
2 00 


2 50 
o 75 


1 50 
5 00 
1 50 


Lodge, 0 . J. Elementary Mechanics.i2moj 

Loewenstein, L. C., and Crissey, C. P. Centrifugal Pumps. . 

Lomax, J. W. Cotton Spinning.i2mo, 

Lord, R. T. Decorative and Fancy Fabrics.8vo, 

Loring, A. E. A Handbook of the Electromagnetic Telegraph, 

i6mo, 

Lowy, A. Organic Type Formulas. o 10 

Lubschez, B. J. Perspective..i2mo, 2 00 


*3 50 


o 75 


3 00 


Lucke, C. E. Gas Engine Design... .8vo, 

-Power Plants: their Design, Efficiency, and Power Costs. 

2 vols.. (In Preparation.) 

Luckiesh, M. Color and Its Application.8vo, *3 50 

-Light and Shade and Their Applications.8vo, *3 00 


-Visual Illusions. (In Preparation.) 

Lunge, G. Coal-tar Ammonia. Three Parts..8vo, *25 00 

-Manufacture of Sulphuric Acid and Alkali. Four Volumes. 

8vo, 

Vol. I. Sulphuric Acid. In three parts. (Reprinting.) 

Vol. I. Supplement. (Reprinting.) 

Vol. II. Salt Cake, Hydrochloric Acid and Leblanc Soda. 

In two parts. ..(In Press.) 

Vol. III. Ammonia Soda. (In Press.)- 

Vol. IV. Electrolytic Methods. (I n Press.) 

-Technical Chemists’ Handbook.i2mo, leather, *4 00 

■-Technical Methods of Chemical Analysis. 

Vol I. In two parts......8vo, (New Edition in Press) 

Vol. II. In two parts.8vo, (New Edition in Press) 

Vol.. III. In two parts.8vo, (New Edition in Press.) 

The set (3 vols.) complete. (i n p re ss ) 


-—Technical Gas Analysis.8vo, 


*4 50 




























D. VAN NOSTRAND COMPANY'S SHORT-TITLE CATALOG 25 


Luquer, L. M. Minerals in Rock Sections. 8 vo, *15° 

b 1 ’ ’ 

MacBride, J. D. A Handbook of Practical Shipbuilding, 

12010, fabrikoid 2 00 

Macewen^II. A. Food Inspection.8vo, *2 50 

Mackenzie, N. F. Notes on Irrigation Works.8vo, *2 50 

Mackie, J. How to Make a Woolen Mill Pay.8vo, *2 00 

Maguire, Wm. R. Domestic Sanitary Drainage and Plumbing 

8vo, 4 00 

Malcolm, H. W. Submarine Telegraph Cable. 90° 

Malinovzsky, A. Analysis of Ceramic Materials and Methods 

of Calculation . {In Press.) 

Mallet, A. Compound Engines.i6mo, 

Mansfield, A. N. Electro-magnets.i6mo, o 75 

Marks, E. C. R. Construction of Cranes and Lifting Machinery 

i2mo, *2 75 

-Manufacture of Iron and Steel Tubes.i2mo, 2 50 

-Mechanical Engineering Materials. i2mo, *1 50 

Marks, G. C. Hydraulic Power Engineering.8vo, 4 50 

Marlow, T. G. Drying Machinery and Practice. .8vo ( Reprinting ) 

Marsh, C. F. Concise Treatise on Reinforced Concrete-8vo, *2 50 

_Reinforced Concrete Compression Member Diagram 

Mounted on Cloth Boards. *1 5 ° 

Marsh, C. F., and Dunn, W. Manual of Reinforced Concrete 

and Concrete Block Construction.i6mo, 2 00 

Marshall, W. J., and Sankey, H. R. Gas Engines.8vo, *2 00 

Martin, G. Triumphs and Wonders of Modern Chemistry. 

8vo, *3 00 

_Modern Chemistry and Its Wonders.8vo, *3 od 

Martin N Properties and Design of Reinforced Concrete, 

8vo, 1 50 

Martin, W. D. Hints to Engineers. I2m °, 2 00 

Massie, W. W., and Underhill, C. R. Wireless Telegraphy and 

Telephony.. *1 00 

Mathot, R. E. Internal Combustion Engines.8vo, 5 00 
























26 D. VAN NOSTRAND COMPANY'S SHORT-TITLE CATALOG 


Maurice, W. Electric Blasting Apparatus and Explosives . . 8 vo, *3 5 c 

-Shot Firer’s Guide. 8 vo, *i 5 c 

Maxwell, F. Sulphitation in White Sugar Manufacture. i2mo, 4 oc 

Maxwell, J. C. Matter and Motion.i6mo, o 75 

Maxwell, W. H., and Brown, J. T. Encyclopedia of Municipal 

and Sanitary Engineering.4to, *10 oc 

Mayer, A. M. Lecture Notes on Physics.8vo, 2 00 

McCracken, E. M., and Sampson, C. H. Course in Pattern 

Making . (In Press.) 

McCullough, E. Practical Surveying....i2mo, 3 oc 

McCullough, R. S. Mechanical Theory of Heat.8vo, 3 5 c 

McGibbon, W. C. Indicator Diagrams for Marine Engineers, 

8vo, *3 5c 

--Marine Engineers’ Drawing Book.oblong 4to, *2 5c 

-Marine Engineers’ Pocketbook.i2mo, leather, *4 50 

McIntosh, J. G. Technology of Sugar.8vo, *6 oc 

-Industrial Alcohol .8vo, *3 5c 

-Manufacture of Varnishes and Kindred Industries. 

Three Volumes. 8vo. 

Vol. I. Oil Crushing, Refining and Boiling. 7 oc 

Vol. II. Varnish Materials and Oil Varnish Making ( Reprinting ) 
Vol. III. Spirit Varnishes and Materials.( Reprinting) 


MeKillop, M., and McKillop, D. A. Efficiency Methods. 


i2mo, 1 5c 

McKnight, J. D., and Brown, A. W. Marine Multitubular 

Boilers . *2 5c 

McMaster, J. B, Bridge and Tunnel Centres......i6mo, o 7; 

McMechen, F. L. Tests for Ores, Minerals and Metals. .i2mo, 1 

McNair, F. V. Handbook for Naval Officers.i2mo, 4 o< 

McNair, Jas. B. Citrus By-Products. (In Press.) 

Meade, A. Modern Gas Works Practice.8vo, *8 5c 

Melick, C. W. Dairy Laboratory Guide.i2mo, *1 2j 


“Mentor.” Self-Instruction for Students in Gas Supply, 

i2mo, 2 5< 

-Advanced Self-Instruction for Students in Gas Supply, 

i2mo, 2 5< 

-Self Instruction for Students in Gas Engineering.i2mo. 























D. VAN NOSTRAND COMPANY'S SHORT-TITLE CATALOG 27 


— Elementary ... 2 00 

— Advanced 
ierivale, J. H. 


2 00 

1 00 

2 00 

3 00 


Notes and Formulae for Mining Students, 

i2mo, 

erritt, Wm. H. Field Testing for Gold and Silver. i6mo, leather, 

[ertens, Colonel. Tactics and Technique in River Crossings. 

Translated by Major Walter Krueger.8vo, 

ierzinski, S. Waterproofing of Fabrics.8vo, *2 50 

iessner, B. F. Radiodynamics.i2mo, *2 00 

iller, G. A. Determinants.i6mo, 

filer, W. J. Historical Geology.i2mo, 

.'ills, C. N. Elementary Mechanics for Engineers-i2mo, 

ilroy, M. E. W. Home Lace-making.i2mo, * 

itchell, C. A. Mineral and Aerated Waters.8vo, 

_and Prideaux, R. M. Fibres Used in Textile and 

Allied Industries .8vo, 

itchell, C. F. and G. A. Building Construction and Draw¬ 
ing.-. i2mo 

— Elementary Course .. • • *. 

— Advanced Course .. 

onckton, C. C. F. Radiotelegraphy.8vo, 

onteverde, R. D. Vest Pocket Glossary of English-Spanish, 

Spanish-English Technical Terms.64mo, leather, 

ontgomery, J. H. Electric Wiring Specifications-i6mo, 

oore, E. C. S. New Tables for the Complete Solution of 
Ganguillet and Kutter’s Formula.8vo, 

oore Harold. Liquid Fuel for Internal Combustion Engines, 

8vo, 5 00 

brecroft, J. H., and Hehre, F. W. Short Course in Electrical 

Testing . 8v0 > 2 00 

organ A P. Wireless Telegraph Apparatus for Amateurs, 

6 ’ i2mo, *1 50 

[organ T D. Principles of Electric Spark Ignition. . .8vo, 3 50 

orrell R. S. and Waele, A. E. Rubber, Resins, Paints and 

’Varnishes . 8v0 Press.) 

oses, A. J. The Characters of Crystals.8vo, *2 00 

__ and Parsons, C. L. Elements of Mineralogy.8vo, 3 50 


2 5c 
1 25 
1 00 

3 00 

3 50 


2 50 
4 50 
*2 00 

1 50 
*1 00 

*6 00 

























28 D. VAN NOSTRAND COMPANY'S SHORT-TITLE CATALOG 


Moss, S. A. Elements of Gas Engine Design.i6mo, o 75 

——The Lay-out of Corliss Valve Gears.i6mo, o 75 

Mulford, A. C. Boundaries and Landmarks.i2mo, *1 00 

Munby, A. E. Chemistry and Physics of Building Materials. 

8vo, 2 50 

Murphy, J. G. Practical Mining. i6mo, 1 00 

Murray, B. M. Chemical Reagents.8vo, 3 00 

Murray, J. A. Soils and Manures.8vo, *2 00 

Nasmith, J. The Student’s Cotton Spinning.8vo, 4 50 

-Recent Cotton Mill Construction.i2mo, 3 00 

Neave, G. B., and Heilbron, I. M. Identification of Organic 

Compounds .i2mo, 1 50 

Neilson, R. M. Aeroplane Patents..8vo, *2 00 

Nerz, F. Searchlights.8vo, ( Reprinting .) 

Newbigin, M. I., and Flett, J. S. James Geikie, the Man 

and the Geologist.8vo, 3 50 


Newbiging, T. Handbook for Gas Engineers and Managers, 


8vo, 7 50 

Newell, F. H., and Drayer, C. E. Engineering as a Career. 

i2mo, cloth, *1 00 

Nicol, G. Ship Construction and Calculation^.8vo, *10 00 

Nipher, F. E. Theory of Magnetic Measurements.i2mo, 1 00 

Nisbet, H. Grammar of Textile Design.8vo, 7 50 

Nolan, H. The Telescope.i6mo, o 75 

Norie, J. W. Epitome of Navigation (2 Vols.).octavo, 15 00 

—1—A Complete Set of Nautical Tables with Explanations 

of Their Use.octavo, 6 50 


North, H. B. Laboratory Experiments in General Chemistry 

i2mo, *1 00 

O’Connor, H. The Gas Engineers’ Pocketbook. ,i2mo, leather, 5 oc 
Ohm, G. S., and Lockwood, T. D. Galvanic Circuit....i6mo, o 75 
Olsen, J. C. Textbook of Quantitative Chemical Analysis. .8vo, 400 

Ormsby, M. T. M. Surveying...i2mo, 2 00 

Oudin, M. A. Standard Polyphase Apparatus and Systems . .8vo, *3 oc 
Owen, D. Recent Physical Research...8vo, 






















D. VAN NOSTRAND COMPANY S SHORT-TITLE CATALOG 29 


Pakes, W. C. C., and Nankivell, A. T. The Science of Hygiene. 

8vo, *i 75 

Palaz, A. Industrial Photometry.8vo, *4 00 

Palmer, A. R. Electrical Experiments.i2mo, o 75 

-Magnetic Measurements and Experiments.i2mo, o 75 

Pamely, C. Colliery Manager’s Handbook.8vo, *10 00 

Parker, P. A. M. The Control of Water.8vo, *6 00 

Parr, G. D. A. Electrical Engineering Measuring Instruments. 

8vo, *3 50 

Parry, E. J. Chemistry of Essential Oils and Artificial Per¬ 
fumes. Two Volumes.8vo. 

Vol. I. Monographs on Essential Oils.,. 9 00 

Vol. II. Constituents of Essential Oils, Analysis. 7 00 

Parry, E J. Foods and Drugs. Two Volumes..8vo, 

Vol. I. Chemical and Microscopical Analysis of Food 

and Drugs ... 9 5 ° 

Vol. II. Sale of Food and Drugs Acts. *3 5° 

-and Coste, J. H. Chemistry of Pigments.8vo, *5 00 

Parry, L. Notes on Alloys.8vo, *3 50 

-Metalliferous Wastes .8vo, *2 50 

-Analysis of Ashes and Alloys.8vo, *2 50 

Parry, L. A. Risk and Dangers of Various Occupations. .8vo, *3 50 
Parshall, H. F., and Hobart, H. M. Electric Railway En¬ 
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Parsons, J. L. Land Drainage.8vo, *1 50 

Parsons, S. J. Malleable Cast Iron.8vo, 3 50 

Partington, J. R. Higher Mathematics for Chemical Students 

i2mo, *2 50 

-The Alkali Industry.8vo, 3 00 

-Textbook of Thermodynamics.8vo, *4 00 

Patchell, W. H. Electric Power in Mines.8vo, *4 00 

Paterson, G. W. L. Wiring Calculations.nmo, *2 50 

-Electric Mine Signalling Installations.i2mo, *1 50 

Patterson, D. The Color Printing of Carpet Yarns.8vo, *3 50 

-Color Matching on Textiles.8vo, *3 50 

-Textile Color Mixing.8vo, *3 50 

Paulding, C. P. Condensation of Steam in Covered and Bare 

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i2mo, *1 00 



































30 D. VAN NOSTRAND COMPANY’S SHORT-TITLE CATALOG 


Payne, D. W. Founders’ Manual.8vo, 

Peddie, R. A. Engineering and Metallurgical Books.. . . i2mo, 

Peirce, B. System of Analytic Mechanics..4to, 

-Linear Associative Algebra.4to, 

Perkin, F. M., and Jaggers, E. M. Elementary Chemistry i2mo, * 

Perrin, J. Atoms.Svo, 

Petit, G. White Lead and Zinc White Paints.8vo, 

Petit, R. How to Build an Aeroplane.8vo, 

Pettit, Lieut. J. S. Graphic Processes.i6mo, 

Philbrick, P. H. Beams and Girders.. ..i6mo, 

Phin, J. Seven Follies of Sciences.nmo, 

Pickworth, C. N. Logarithms for Beginners. .. .i2mo, boards, 


Pilcher, R. B., and Butler-Jones, F. 

to Chemical Science. 


Plympton, G. W. 
-How to Beco 


Pochet, M. L. Steal 
Pocket Logarithms 


to 


Popplewell, W. C. 


*4 oo 
*i 50 
10 00 
2 50 
1 00 
*2 50 
*2 00 

*1 50 
o 75 

*1 50 

I 00 yr 


Pratt. 


i2mo, 

1 

50 

i2mo, 

2 

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i2mo, 

1 

50 

a, re- 




*4 

00 

i6mo, 

0 

75 

i6mo, 

0 

75 

i6mo, 

0 

75 

i6mo, 

0 

75 

i6mo, 

0 

75 

ither, 

1 

00 

s. 8vo, 

*3 

50 

. .8vo, 

10 

00 

i2mo, 

3 

00 

8vo, 

1 

50 


*3 

50 


*2 

50 

i2mo, 

*1 

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i2mo, 

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50 

. .8vo, 

*2 

50 

.. 8vo, 

*3 

50 


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-Graphical Determination of Earth Slopes. 8vo, *2 00 

-Tunneling.8vo, *3 00 

-Dredging. A Practical Treatise.8vo, *3 00 

Prescott, A. B., and Johnson, 0 . C. Qualitative Chemical 

Analysis . 8vo, 4 00 

-and Sullivan, E. C. First Book in Qualitative Chemistry 

i2mo, *1 50 

Prideaux, E. B. R. Problems in Physical Chemistry.8vo, *2 00 

-Theory and Usb of Indicators.8vo, 5 00 

Prince, G. T. Flow of Water.nmo, *2 00 

Pull, Ernest. Modern Steam Boilers.8vo, 5 00 

Pullen, W. W. F. Application of Graphic Methods to the Design 

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-Injectors: Theory, Construction and Working. ...i2mo, *2 00 

-Indicator Diagrams.8vo, 3 00 

-Engine Testing .8vo, *5 50 

Purday, H. F. P. Diesel Engine Design.8vo, 7 50 

Putsch, A. Gas and Coal-dust Firing.8vo, *2 50 

Rafter, G. W. Mechanics of Ventilation...i6mo, o 75 

-Potable Water .i6mo, o 75 

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4to, *6 00 

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Randau, P. Enamels and Enamelling.8vo, *5 00 

Rankine, W. J. M. Applied Mechanics..8vo, 6 00 

-Civil Engineering .8vo, 7 50 

-Machinery and Millwork.8vo, 6 00 

_The Steam-engine and Other Prime Movers.8vo, 6 00 

--and Bamber, E. F. A Mechanical Textbook.8vo, 4 00 

Raphael, F. C. Localization of Faults in Electric Light and 

Power Mains.8vo, *3 50 

Rasch, E. Electric Arc Phenomena.8vo, *2 00 

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32 D. VAN NOSTRAND COMPANY'S SHORT-TITLE CATALOG 

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Raut^nstrauch, W. Notes on the Elements of Machine Design, 

8 vo, boards, *1 50 

Rautenstrauch, W., and Williams, J. T. Machine Drafting and 


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Raymond, E. B. Alternating Current Engineering.i2mo, *2 50 

Rayner, H. Silk Throwing and Waste Silk Spinning. . .8vo, 

Recipes for the Color, Paint, Varnish, Oil, Soap and Drysaltery 

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Redfern, J B., and Savin, J. Bells, Telephones.i6mo, o 75 

Redgrove, H. S. Experimental Mensuration.i2mo, *1 50 

Reed, S. Turbines Applied to Marine Propulsion. *5 00 

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-Useful Hints to Sea-going Engineers.i2mo, 3 00 

Reid, E. E. Introduction to Research in Organic Chemistry. 

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Reiser, F. Hardening and Tempering of Steel.i2mo, *2 50 

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Reuleaux, F. The Constructor.4to, *4 00 

Rey, J. Range of Electric Searchlight Projectors. .8vo, {Reprinting.) 
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Rhodes, H. J. Art of Lithography. 8 vo, 5 00 

Rice, J. M., and Johnson, W. W. A New Method of Obtaining 

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Richards, W. A. Forging of Iron and Steel.izmo, 2 25 

Richards, W. A., and North, H. B. Manual of Cement Testing, 

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Richardson, J. The Modern Steam Engine.8vo, *3 5 ® 

Richardson, S. S. Magnetism and Electricity.ismo, *200 

Rideal, E. K. Industrial Electrometallurgy.8vo, 3 00 

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Rideal, S. Glue and Glue Testing.8vo, *5 00 

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Riesenberg, F. The Men on Deck. I2m0 > 3 00 

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Rimmer, E. J. Boiler Explosions, Collapses and Mishaps.8vo, 2 25 

Rings, F. Concrete in Theory and Practice.i2mo, *4 5 ° 

_Reinforced Concrete Bridges.4to, *5 00 


Ripper, W. Course of Instruction in Machine Drawing., .folio, 

Roberts, F. C. Figure of the Earth.i6mo, 

Roberts, J., Jr. Laboratory Work in Electrical Engineering 

8vo, 


Robertson, J. B. The Chemistry of Coal.✓.” s m °, 

Robertson, L. S. Water-tube Boilers.8vo, 

Robinson, J. B. Architectural Composition. ....... • •• -8vo, 

Robinson, S. W. Practical Treatise on the Teeth of Wheels. 

i6mo, 

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_Wrought Iron Bridge Members.i6mo, 

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Roebling, J. A. Long and Short Span Railway Bridges folio, 
Rogers, A. A Laboratory Guide of Industrial Chemistry. 8vo, 

_-Elements of Industrial Chemistry. I2mo > 

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*6 00 
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34 D. VAN NOSTRAND COMPANY^ SHORT-TITLE CATALOG 

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Rose, T. K. The Precious Metals.8vo, 2 50 

Rosenhain, W. Glass Manufacture.. 8 vo, 4 00 

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Roth, W. A. Physical Chemistry.8vo, *2 00 

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Ruhmer, E. Wireless Telephony.8vo, *4 50 

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Rust, A. Practical Tables for Navigators and Aviators,. 8vo, 3 50 

Rutley, F. Elements of Mineralogy. i2mo, 2 50 

Sandeman, E. A. The Manufacture of Earthenware. .i2mo, 3 50 

Sanford, P. G. Nitro-explosives.8vo, *400 

Saunders, C. H. Handbook of Practical Mechanics-i6mo, 1 50 

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Sayers, H. M. Brakes for Tram Cars..8vo, *1 25 

Schaefer, C. T. Motor Truck Design.8vo, 2 50 

Scheele, C. W. Chemical Essays.8vo, *2 50 

Scheithauer, W. Shale Oils and Tars.8vo, *4 00 

Scherer, R. Casein. 8 vo, *3 5 ° 


Schidrowitz, P. Rubber, Its Production and Industrial Uses, 

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Schwartz, E. H. L. Causal Geology.8vo, *3 00 

Schweizer, V. Distillation of Resins..8vo, *5 00 

Scott, A. H. Reinforced Concrete in Practice......i2mo, 200 


























D. VAN NOSTRAND COMPANY^ SHORT-TITLE CATALOG 35 


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i6mo, leather, 1 50 

Scudder, H. Electrical Conductivity and Ionization Constants 

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Searle, A. B. Modern Brickmaking.8vo, 7 00 

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Searle, G. M. “ Sumners’ Method.” Condensed and Improved. 


i6mo, o 75 

Seaton, A. E. Manual of Marine Engineering.8vo, 10 00 

Seaton, A. E., and Rounthwaite, H. M. Pocket-book of Marine 

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Seidell, A. Solubilities of Inorganic and Organic Substances, 

8vo, *7 50 

Sellew, W. H. Steel Rails...4to, *10 00 

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Senter, G. Outlines of Physical Chemistry.i2mo, 3 00 

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Sexton, A. H. Fuel and Refractory Materials. . 12010, ( Reprinting .) 

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Shaw, Henry S. H. Mechanical Integrators.i6mo, o 75 

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Shields, J. E. Note on Engineering Construction.i2mo, 1 50 

Shreve, S. H. Strength of Bridges and Roofs.8vo, 3 50 

Shunk, W. F. The Field Engineer.. .. ,i2mo, fabrikoid, 3 00 

Silverman, A., and Harvey, A. W. Laboratory Directions and 
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Simpson, G. The Naval Constructor.nmo, fabrikoid, *5 00 

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Thompson, S. P. Dynamo Electric Machines.i6mo, o 75 

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Turnbull, Jr., J., and Robinson, S. W. A Treatise on the 

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Vega, Baron, Von. Logarithmic Tables-.8vo, 2 50 

Vincent, C.. Ammonia and Its Compounds. 8vo, *2 50 

Virgin, R. Z. Coal Mine Management. (In Press.) 
























D VAN NOSTRAND COMPANY^ SHORT-TITLE CATALOG 41 


Volk, C. Haulage and Winding Appliances. 8 vo, *4 °° 

Von Georgievics, G. Chemical Technology of Textile Fibres. 

8vo, 7 00 

Chemistry of Dyestuffs. 8vo. (New Edition in Preparation.) 
v ose, G. L. Graphic Method for Solving Certain Questions in 


Arithmetic and Algebra...i6mo, 0 75 

Vosmaer, A. Ozone. 8v0 > 2 5 ° 


Wabner, R. Ventilation in Mines.....8vo, *500 

Wadmore, J. M. Elementary Chemical Theory.i2mo, *1 50 

Wagner, E. Preserving Fruits, Vegetables, and Meat..i2mo, *2 50 
Wagner, H. E., and Edwards, H. W. Railway Engineering 

Estimates . Press.) 


Wagner, J. B. Seasoning of Wood..8vo, 4 00 

Waldram, P. J. Principles of Structural Mechanics. .. i2mo, 4 00 

Walker, F. Dynamo Building.i6mo, o 75 

Walker, J. Organic Chemistry for Students of Medicine.8vo, 4 00 

Walker’ S. F. Refrigeration, Heating and Ventilation on 

’ Shipboard .i2mo, jz 50 

_Electricity in Mining. 8 vo, 4 50 

__Electric Wiring and Fitting.8vo, 2 50 

Wallis-Tayler, A. J. Bearings and Lubrication.... .8vo, *1 50 

_serial or Wire Ropeways.8vo, 5 00 

-Preservation of Wood.8vo, 4 00 

_Refrigeration, Cold Storage and Ice Making.8vo, 5 50 

--Sugar Machinery.121110, 3 00 

Walsh J. J. Chemistry and Physics of Mining and Mine 

Ventilation .. 2 50 

Wanklyn, J. A. Water Analysis. I2m0 > 2 00 


-Slide Valves . 

Waring, Jr., G. E. 


_How to Drain a House 

Warnes^ A. R. Coal Tar D 
Warren, F. D. Handbook or 
Watkins, A. Photography. 


i2mo, 

*2 

50 

. i2mo, 

*2 

00 

. i6mo, 

0 

75 


*6 

00 

. i2mo, 

2 

00 

.i2mo, 

1 

25 

.. .8vo, 

*5 

00 

. i2mo, 

*2 

50 


3 

00 

































42 D. VAN NOSTRAND COMPANY’S SHORT-TITLE CATALOG 


1 25 

5 00 

2 00 
1 00 

4 00 

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3 75 

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5 00 
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3 00 


Watson, E. P. Small Engines and Boilers.. .i2mo, 

Watt, A. Electro-plating and Electro-refining of Metals.8vo, 

-Electro-plating .i2mo, 

-Electro-metallurgy .i2mo, 

-The Art of Soap-making.8vo, 

-Leather Manufacture .8vo, 

-Paper Making .8vo, 

Webb, H. L. Guide to the Testing of Insulated Wires and 

Cables .ismo, 

Wegmann, E. Conveyance and Distribution of Water for 

Water Supply.8vo, 

Weisbach, J. A Manual of Theoretical Mechanics.8vo, 

-and Herrmann, G. Mechanics of Air Machinery... .8vo, 

Wells, Robt. Ornamental Confectionery.nmo, 

Weston, E. B. Loss of Head Due to Friction of Water in Pipes, 

i2mo, 2 00 

Wheatley, 0 . Ornamental Cement Work.8vo, *2 25 

Whipple, S. An Elementary and Practical Treatise on Bridge 

Building .8vo, 3 00 

White, C. H. Methods in Metallurgical Analysis-i2mo, 3 00 

White, G. F. Qualitative Chemical Analysis.i2mo, 1 40 

White, G. T. Toothed Gearing.i2mo, *2 00 

White, H. J. Oil Tank Steamers.i2mo, 3 00 

Whitelaw, John. Surveying.8vo, 4 50 

Whittaker, C. M. Application of the Coal Tar Dyestuffs. 8vo, 3 00 

Widmer, E. J. Observation Balloons.nmo, 3 00 

Wilcox, R. M. Cantilever Bridges. i6mo, o 75 

Wilda, H. Steam Turbines.i2mo, *2 00 

-Cranes and Hoists.nmo, *2 00 

Wilkinson, H. D. Submarine Cable Laying and Repairing, 

8vo ( Reprinting ) 

Williamson, J. Surveying.8vo, *3 00 

Williamson, R. S. Practical Tables in Meteorology and 

Hypsometry .4to, 2 5a 

Wilson, F. J., and Heilbron, I. M. Chemical Theory and Cal¬ 
culations .nmo, 1 75 

Wilson, J. F. Essentials of Electrical Engineering.8vo, 2 50 

Wimperis, H. E. Internal Combustion Engine.8vo, 3 50 

-Application of Power to Road Transport.i2mo, *1 50 

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D. VAN NOSTRAND COMPANY’S SHORT-TITLE CATALOG 43 


Winchell, N. H., and A. N. Elements of Optical Mineralogy 8vo, *3 5 “ 


Winslow, A. Stadia Surveying.i6mo, o 75 

Wisser, Lieut. J. P. Explosive Materials.i6mo, 

-Modern Gun Cotton.i6mo, o 75 

Wolff, C. E. Modern Locomotive Practice.8vo, *4 20 

Wood, De V. Luminiferous Aether.i6mo, 75 

Wood, J. K. Chemistry of Dyeing. I2m0 > 1 00 

Worden, E. C. The Nitrocellulose Industry. Two vols..8vo, *10 00 
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Vol. VIII. Cellulose Acetate. *5 00 


Wren, H. Organometallic Compounds of Zinc and Magnesium. 

* i2mo, *1 00 

-Simple Method for Testing Painter’s Materials.... 8vo, *2 50 

Wright. A. C. Simple Method for Testing Painters 

Materials .. - 8 ™’. 2 5 ° 

Wright F W. Design of a Condensing Plant..i2mo, ( Reprinting.) 
Wright, J. Testing, Fault Finding, etc., for Wiremen. .i6mo, *0 50 

Wright, T. W. Elements of Mechanics. 8vo , * 2 5<> 

_and Hayford, J. F. Adjustment of Observations .... .8vo, *3 00 

Wynne W E., and Spraragen, W. Handbook of Engineering 

Mathematics . I2mo . leather > * 2 00 


Yoder, J. H. and Wharen, G. B. Locomotive Valves and 

’ Valve Gears. 8v0 > 

Young, J. E. Electrical Testing for Telegraph Engineers... 8vo, 

Young! R. B. The Banket. •••••. . 8 ™’ 

Youngson, P. Slide Valve and Valve Gearing.4to, 


3 oo 
*4 oo 
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Zahner, R. Transmission of Power. l6m0 ’ 

Zeuner A. Technical Thermodynamics. Two Volumes. .8vo, 
Zimmer, G. F. Mechanical Handling and Storing of Materials, 


•:_Mechanical Handling bf Material and Its National Im¬ 
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Zipser, J. Textile Raw Materials.'i; 8 ™’ 

Zur Nedden, F. Engineering Workshop Machines and Proc¬ 
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*8 oo 

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*2 00 


























D.Van nostrand Company 


are prepared to supply, either from 
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short notice. 

Any Technical or 

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In addition to publishing a very large 
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Company have on hand the largest 
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All inquiries are cheerfully and care¬ 
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8 Warren Street - - New York 


aw 


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